U.S. patent application number 16/934146 was filed with the patent office on 2020-11-05 for apparatus and methods for electromagnetic heating of hydrocarbon formations.
The applicant listed for this patent is Acceleware Ltd.. Invention is credited to Geoff Clark, Michal M. Okoniewski, Damir Pasalic, Pedro Vaca.
Application Number | 20200347709 16/934146 |
Document ID | / |
Family ID | 1000004969906 |
Filed Date | 2020-11-05 |
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United States Patent
Application |
20200347709 |
Kind Code |
A1 |
Okoniewski; Michal M. ; et
al. |
November 5, 2020 |
APPARATUS AND METHODS FOR ELECTROMAGNETIC HEATING OF HYDROCARBON
FORMATIONS
Abstract
An apparatus and method for electromagnetic heating of a
hydrocarbon formation. The method involves providing electrical
power to at least one electromagnetic wave generator for generating
high frequency alternating current; using the electromagnetic wave
generator to generate high frequency alternating current; using at
least one pipe to define at least one of at least two transmission
line conductors; coupling the transmission line conductors to the
electromagnetic wave generator; and applying the high frequency
alternating current to excite the transmission line conductors. The
excitation of the transmission line conductors can propagate an
electromagnetic wave within the hydrocarbon formation. In some
embodiments, the method further comprises determining that a
hydrocarbon formation between the transmission line conductors is
at least substantially desiccated; and applying a radiofrequency
electromagnetic current to excite the transmission line conductors.
The radiofrequency electromagnetic current radiates to a
hydrocarbon formation surrounding the transmission line
conductors.
Inventors: |
Okoniewski; Michal M.;
(Calgary, CA) ; Pasalic; Damir; (Calgary, CA)
; Vaca; Pedro; (Calgary, CA) ; Clark; Geoff;
(Calgary, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Acceleware Ltd. |
Calgary |
|
CA |
|
|
Family ID: |
1000004969906 |
Appl. No.: |
16/934146 |
Filed: |
July 21, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16092335 |
Oct 9, 2018 |
10760392 |
|
|
PCT/CA2017/050437 |
Apr 10, 2017 |
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16934146 |
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62409079 |
Oct 17, 2016 |
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62321880 |
Apr 13, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B 6/50 20130101; H05B
2214/03 20130101; E21B 36/04 20130101; E21B 43/2408 20130101; H05B
6/62 20130101; E21B 43/2401 20130101; H05B 6/46 20130101; H05B 6/52
20130101 |
International
Class: |
E21B 43/24 20060101
E21B043/24; H05B 6/52 20060101 H05B006/52; H05B 6/46 20060101
H05B006/46; E21B 36/04 20060101 E21B036/04; H05B 6/50 20060101
H05B006/50; H05B 6/62 20060101 H05B006/62 |
Claims
1. An apparatus for electromagnetic heating of a hydrocarbon
formation, the apparatus comprising: an electrical power source; at
least one electromagnetic power source for generating a
time-varying current or voltage, the at least one electromagnetic
power source being powered by the electrical power source; and at
least one transmission line being coupled to the at least one
electromagnetic power source, the at least one transmission line
having at least two transmission line conductors, the at least one
transmission line conductor having a proximal end and a distal end,
the at least one transmission line being excitable by the
time-varying current or voltage to propagate an electromagnetic
wave from the proximal end of the at least one transmission line
toward the distal end of the at least one transmission line within
the hydrocarbon formation.
2. The apparatus of claim 1, further comprising at least one
waveguide for carrying the time-varying current or voltage from the
at least one electromagnetic power source to the at least one
transmission line, each of the at least one waveguide having a
proximal waveguide end and a distal waveguide end, the proximal
waveguide end of the at least one waveguide being connected to the
at least one electromagnetic power source, the distal waveguide end
of the at least one waveguide being connected to at least one of
the at least two transmission line conductors.
3. The apparatus of claim 2 further comprising at least one choke
coupled to the at least one waveguide for blocking a substantial
portion of the time-varying current or voltage that is reflected at
the distal end of the at least one transmission line from
travelling on external surfaces of the at least one waveguide in a
direction away from the at least one transmission line.
4. The apparatus of claim 2, wherein the at least one waveguide
comprises a first waveguide and a second waveguide, the first
waveguide being a first coaxial transmission line comprising a
first outer conductor coaxially surrounding a first inner
conductor, the second waveguide being a second coaxial transmission
line comprising a second outer conductor coaxially surrounding a
second inner conductor.
5. The apparatus of claim 4, wherein the first outer conductor is
in electrical contact with the second outer conductor for blocking
a substantial portion of the time-varying current or voltage that
is reflected at the distal end of the at least one transmission
line from travelling on external surfaces of at least one of the
first outer conductor or the second outer conductor in a direction
away from the at least one transmission line.
6. The apparatus of claim 4, further comprising dielectric gas
between at least one of the first inner conductor and the first
outer conductor of the first coaxial transmission line or the
second inner conductor and the second outer conductor of the second
coaxial transmission line.
7. The apparatus of claim 4, wherein further comprising at least
one centralizer disposed between the first inner conductor and the
first outer conductor of the first coaxial transmission line or the
second inner conductor and the second outer conductor of the second
coaxial transmission line.
8. The apparatus of claim 1, wherein the time-varying current or
voltage comprises a periodic signal having a fundamental frequency
between about 1 kilohertz (kHz) to about 10 megahertz (MHz).
9. The apparatus of claim 1 further comprises electrical insulation
disposed along at least part of a length of a transmission line
conductor for electrically insulating the transmission line
conductor.
10. A method for electromagnetic heating of a hydrocarbon formation
comprising: providing electrical power to at least one
electromagnetic power source for generating a time-varying current
or voltage; providing at least one transmission line, the at least
one transmission line having at least two transmission line
conductors, the at least one transmission line having a proximal
end and a distal end; coupling the at least one transmission line
to the at least one electromagnetic power source; using the at
least one electromagnetic power source to generate the time-varying
current or voltage; and applying the time-varying current or
voltage to excite the at least one transmission line, the
excitation of the at least one transmission line being capable of
propagating an electromagnetic wave from the proximal end of the at
least one transmission line toward the distal end of the at least
one transmission line within the hydrocarbon formation.
11. The method of claim 10, wherein: coupling the at least two
transmission line conductors to the at least one electromagnetic
power source comprises: providing at least one waveguide, each of
the at least one waveguide having a proximal waveguide end and a
distal waveguide end; connecting the at least one proximal
waveguide end of the at least one waveguide to the at least one
electromagnetic power source; and connecting the at least one
distal waveguide end of the at least one waveguide to at least one
of the at least two transmission line conductors; and applying the
time-varying current or voltage to excite the at least one
transmission line comprises using the at least one waveguide to
carry time-varying current or voltage from the at least one
electromagnetic power source to the at least two transmission line
conductors.
12. The method of claim 11, further comprises coupling at least one
choke to the at least one waveguide for blocking a substantial
portion of the time-varying current or voltage that is reflected at
the distal end of the at least one transmission line from
travelling on external surfaces of the at least one waveguide in a
direction away from the at least one transmission line.
13. The method of claim 11, wherein providing at least one
waveguide comprises providing a first waveguide and a second
waveguide, the first waveguide being a first coaxial transmission
line comprising a first outer conductor coaxially surrounding a
first inner conductor, the second waveguide being a second coaxial
transmission line comprising a second outer conductor coaxially
surrounding a second inner conductor.
14. The method of claim 13, wherein providing at least one
waveguide comprises providing electrical contact between the first
outer conductor and the second outer conductor for blocking a
substantial portion of the time-varying current or voltage that is
reflected at the distal end of the at least one transmission line
from travelling on external surfaces of at least one of the first
outer conductor or the second outer conductor in a direction away
from the at least one transmission line.
15. The method of claim 13, further comprises providing a
dielectric gas between at least one of the first inner conductor
and the first outer conductor of the first coaxial transmission
line or the second inner conductor and the second outer conductor
of the second coaxial transmission line.
16. The method of claim 13, further comprises disposing at least
one centralizer between the first inner conductor and the first
outer conductor of the first coaxial transmission line or the
second inner conductor and the second outer conductor of the second
coaxial transmission line.
17. The method of claim 10, wherein the time-varying current or
voltage comprises a periodic signal having a fundamental frequency
between about 1 kilohertz (kHz) to about 10 megahertz (MHz).
18. The method of claim 10, further comprises disposing electrical
insulation along at least part of a length of that transmission
line conductor for electrically insulating the transmission line
conductor.
19. The method of claim 11, further comprises: determining that a
hydrocarbon formation between the at least one transmission line is
at least substantially desiccated; and applying an electromagnetic
current or voltage to excite the at least one transmission line to
induce electromagnetic waves radiating from the at least one
transmission line to a hydrocarbon formation surrounding the at
least one transmission line, the electromagnetic current having a
fundamental frequency between about 1 kilohertz (kHz) to about 10
megahertz (MHz).
20. The method of claim 19, wherein determining that a hydrocarbon
formation between the at least one transmission line is at least
substantially desiccated comprises either: measuring impedance at
the proximal end of the at least one waveguide; and if the
impedance is within a threshold impedance, determining that the
hydrocarbon formation between the at least one transmission line is
desiccated; otherwise determining that the hydrocarbon formation
between the at least one transmission line is not desiccated; or
defining at least one temperature measurement location within the
hydrocarbon formation between the at least one transmission line;
obtaining at least one temperature measurement at each of the at
least one temperature measurement locations; and for each of the at
least one temperature measurement locations, if the temperature at
that temperature measurement location is above a steam saturation
temperature, determining that the hydrocarbon formation at that
temperature measurement location is desiccated; otherwise
determining that the hydrocarbon at that temperature measurement
location is not desiccated.
Description
FIELD
[0001] The embodiments described herein relate to the field of
heating hydrocarbon formations, and in particular to apparatus and
methods for electromagnetically heating hydrocarbon formations.
BACKGROUND
[0002] Electromagnetic (EM) heating can be used for enhanced
recovery of hydrocarbons from underground reservoirs. Similar to
traditional steam-based technologies, the application of EM energy
to heat hydrocarbon formations can reduce viscosity and mobilize
bitumen and heavy oil within the hydrocarbon formation for
production. However, the use of EM heating can require less fresh
water than traditional steam-based technologies. As well, the heat
transfer with EM heating can be more efficient than that of
traditional steam-based technologies, leading to lower capital and
operational expenses. The lower cost of EM heating provides the
potential to unlock oil reservoirs that would otherwise be unviable
or uneconomical for production with steam-based technologies such
as shallow formations, thin formations, formations with thick shale
layers, and mine-face accessible hydrocarbon formations for
example. Hydrocarbon formations can include heavy oil formations,
oil sands, tar sands, carbonate formations, sale oil formations,
and other hydrocarbon bearing formations.
[0003] EM heating of hydrocarbon formations can be achieved by
using an EM radiator, or antenna, or applicator, positioned inside
an underground reservoir to radiate EM energy to the hydrocarbon
formation. The antenna is typically operated resonantly. The
antenna can receive EM power generated by an EM wave generator, or
radio frequency (RF) generator, located above ground. The EM wave
generator typically generates power in the radio frequency range of
300 kHz to 300 MHz.
[0004] As the hydrocarbon formation is heated, the characteristics
of the hydrocarbon formation, and in particular, the impedance,
change. In order to maintain efficient power transfer to the
hydrocarbon formation, dynamic or static impedance matching
networks can be used between the antenna and the RF generator to
limit the reflection of EM power from the antenna back to the RF
generator. As well, the RF generator can be adjusted to limit the
reflection of EM power from the antenna back to the RF generator.
Such operational adjustments and impedance matching networks
increase operational, equipment, and design costs.
[0005] To carry EM power from an RF generator to the antenna, RF
transmission lines capable of delivering high EM power over long
distances and capable of withstanding harsh environments (e.g.,
such as high pressure and temperature) usually found within oil
wells are required. However, most commercially available low
diameter RF transmission lines are currently limited to delivering
low or medium EM power over long distances and rated for lower
pressure and temperature than that usually found within oil wells.
High power transmission lines such as rectangular waveguides are
too large for practical deployment at the frequency range of
interest. The cost of currently available RF generators is also
high when measured on a cost per RF watt generated basis.
[0006] Antennas are typically dipole antennas, which require an
electrically lossless or at least low loss region around the two
dipole arms. Methods to provide such a lossless region, such as
providing electrically lossless material, providing electrically
lossless coatings, or forming a lossless region within the
hydrocarbon formation, can be complex, expensive, or
time-consuming. Furthermore, antenna components typically require
electrical isolation, which adds complexity to maintaining
mechanical integrity.
[0007] Underground antennas generally have short penetration range
and hence most of their electromagnetic power is dissipated within
a short distance from the antenna. That is, antennas generally heat
formations in the range of less than a wavelength, or a few
wavelengths of the operating frequency of the antenna.
SUMMARY
[0008] According to some embodiments, there is an apparatus for
electromagnetic heating of a hydrocarbon formation. The apparatus
comprises an electrical power source, at least one electromagnetic
wave generator for generating high frequency alternating current,
and at least two transmission line conductors coupled to the at
least one electromagnetic wave generator. The at least one
electromagnetic wave generator is powered by the electrical power
source. The at least two transmission line conductors can be
excited by the high frequency alternating current to propagate an
electromagnetic wave within the hydrocarbon formation. At least one
transmission line conductor is defined by a pipe.
[0009] The apparatus may further comprise at least one waveguide
for carrying high frequency alternating current from the at least
one electromagnetic wave generator to the at least two transmission
line conductors. Each of the at least one waveguide has a proximal
end and a distal end. The proximal end of the at least one
waveguide is connected to the at least one electromagnetic wave
generator. The distal end of the at least one waveguide is
connected to one of the at least two transmission line
conductors.
[0010] The at least one waveguide may comprise at least one of a
power cable, a coaxial transmission line, a wire, a pipe, and at
least one conductor.
[0011] The high frequency alternating current may have a frequency
between about 1 kilohertz (kHz) to about 10 megahertz (MHz).
[0012] The pipe defining a transmission line conductor may comprise
an interior cavity usable for conveying fluids.
[0013] The pipe defining a transmission line conductor may comprise
coiled tubing.
[0014] Each of the at least one transmission line conductor defined
by a pipe may comprise an external surface of the pipe.
[0015] The pipe may have a pipe opening for connecting a distal end
of the at least one waveguide to the external surface of that pipe.
The pipe opening may be formed by removing a segment of that
pipe.
[0016] The pipe opening may be plugged with insulating material for
blocking substances from entering the pipe.
[0017] In some embodiments when the at least one waveguide is a
first coaxial transmission line, the first coaxial transmission
line may include a first outer conductor and a first inner
conductor, the first inner conductor being concentrically
surrounded by the first outer conductor.
[0018] In some embodiments, the first coaxial transmission line may
further include dielectric gas between the first inner conductor
and the first outer conductor.
[0019] In some embodiments, the first coaxial transmission line may
further include at least one of a circulation system and a
pressurization system, the circulation system for circulating the
dielectric gas within the first coaxial transmission line, and the
pressurization system for maintaining pressure of the dielectric
gas within the first coaxial transmission line.
[0020] The at least one waveguide may further comprise a second
coaxial transmission line. The second coaxial transmission line may
comprise a second outer conductor. The first outer conductor may be
in electrical contact with the second outer conductor for blocking
a substantial portion of the high frequency alternating current
from travelling on external surfaces of at least one of the first
outer conductor and the second outer conductor in a direction away
from the at least two transmission line conductors.
[0021] In some embodiments, the first coaxial transmission line may
further include at least one dielectric layer disposed between the
first inner conductor and the first outer conductor for
electromagnetically isolating the first inner conductor.
[0022] In some embodiments, the first coaxial transmission line may
further include a centralizer connecting the first inner conductor
and the first outer conductor for cooling the first inner
conductor.
[0023] In some embodiments, the first outer conductor may comprise
at least one casing pipe and the first inner conductor may comprise
at least one of a producer pipe and an injector pipe.
[0024] The at least one casing pipe may be electrically grounded
for blocking a substantial portion of the high frequency
alternating current from travelling on an external surface of the
at least one casing pipe in a direction away from the at least two
transmission line conductors.
[0025] The apparatus may further comprise a separation medium for
electrically isolating the at least one casing pipe. The separation
medium may concentrically surround at least part of a length of the
at least one casing pipe.
[0026] The apparatus may further comprise at least one choke, the
at least one choke for blocking a substantial portion of the high
frequency alternating current from travelling on external surfaces
of the at least one waveguide in a direction away from the at least
two transmission line conductors.
[0027] The apparatus may further comprise electrical insulation
disposed along at least part of a length of a transmission line
conductor for electrically insulating the transmission line
conductor.
[0028] The at least one electromagnetic wave generator may comprise
a first electromagnetic wave generator and a second electromagnetic
wave generator. The at least two transmission line conductors may
comprise a first pair of transmission line conductors and a second
pair of transmission line conductors. The first pair of
transmission line conductors may be excitable by high frequency
alternating current generated by the first electromagnetic wave
generator and the second pair of transmission line conductors may
be excitable by high frequency alternating current generated by the
second electromagnetic wave generator. In some embodiments, the
high frequency alternating current generated by the first
electromagnetic wave generator may be about 180.degree. out of
phase with the high frequency alternating current generated by the
second electromagnetic wave generator. In other embodiments, the
high frequency alternating current generated by the first
electromagnetic wave generator may be substantially in phase with
the high frequency alternating current generated by the second
electromagnetic wave generator.
[0029] According to some embodiments, there is a method for
electromagnetic heating of a hydrocarbon formation. The method
comprises providing electrical power to at least one
electromagnetic wave generator for generating high frequency
alternating current; using the electromagnetic wave generator to
generate high frequency alternating current; using at least one
pipe to define at least one of at least two transmission line
conductors; coupling the transmission line conductors to the
electromagnetic wave generator; and applying the high frequency
alternating current to excite the transmission line conductors. The
excitation of the transmission line conductors can propagate an
electromagnetic wave within the hydrocarbon formation.
[0030] The method may further comprise determining that a
hydrocarbon formation between the transmission line conductors is
at least substantially desiccated; and applying a radiofrequency
electromagnetic current to excite the transmission line conductors.
Electromagnetic waves from the radiofrequency electromagnetic
current can radiate to a hydrocarbon formation surrounding the
transmission line conductors.
[0031] Further aspects and advantages of the embodiments described
herein will appear from the following description taken together
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] For a better understanding of the embodiments described
herein and to show more clearly how they may be carried into
effect, reference will now be made, by way of example only, to the
accompanying drawings which show at least one exemplary embodiment,
and in which:
[0033] FIG. 1 is profile view of an apparatus for electromagnetic
heating of formations according to one embodiment;
[0034] FIG. 2 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0035] FIG. 3 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0036] FIG. 4 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0037] FIG. 5 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0038] FIG. 6 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0039] FIG. 7 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0040] FIG. 8 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0041] FIG. 9 is a profile view of an apparatus for electromagnetic
heating of formations according to another embodiment;
[0042] FIG. 10 is a profile view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0043] FIGS. 11A to 11D are cross-sectional view of transmission
line conductors and outer waveguide conductors according to at
least one example embodiment;
[0044] FIGS. 12A to 12B are cross-sectional view of transmission
line conductors according to at least one example embodiment;
[0045] FIG. 13 is a schematic view of an apparatus having five
transmission line conductor pairs and one EM wave generator;
[0046] FIGS. 14 and 15 are profile and cross-sectional views of an
apparatus for electromagnetic heating of formations according to
another embodiment;
[0047] FIGS. 16 and 17 are profile and cross-sectional views of an
apparatus for electromagnetic heating of formations according to
another embodiment;
[0048] FIGS. 18 and 19 are profile and cross-sectional views of an
apparatus for electromagnetic heating of formations according to
another embodiment;
[0049] FIGS. 20 and 21 are profile and cross-sectional views of an
apparatus for electromagnetic heating of formations according to
another embodiment;
[0050] FIG. 22 is a profile view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0051] FIG. 23A is a cross-sectional view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0052] FIG. 23B is a cross-sectional view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0053] FIG. 24A is a cross-sectional view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0054] FIG. 24B is a cross-sectional view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0055] FIG. 25A is a magnified cross-sectional view of a portion of
an apparatus for electromagnetic heating of formations according to
the embodiments shown in FIGS. 15, 17, and 21;
[0056] FIG. 25B is a magnified cross-sectional view of a portion of
an apparatus for electromagnetic heating of formations according to
the embodiments shown in FIGS. 23A, 23B, and 24;
[0057] FIG. 26 is a profile view of the deployment of coiled tubing
for an apparatus for electromagnetic heating of formations
according to at least one embodiment;
[0058] FIG. 27 is a profile view of an apparatus with exposed
transmission line conductors operating as an open transmission line
according to at least one example embodiment;
[0059] FIG. 28 is a profile view of an apparatus with insulated
transmission line conductors operating as an open transmission line
according to at least one example embodiment;
[0060] FIGS. 29 and 30 are profile views of an apparatus operating
as an open transmission line and a leaky wave antenna according to
at least one example embodiment;
[0061] FIGS. 31A to 31C are temperature distributions of an
insulated dynamic transmission line after 20, 50, and 90 days;
[0062] FIGS. 32A to 32C are heat delivery distributions of a
non-insulated dynamic transmission line after 1, 100, and 200
days;
[0063] FIGS. 33A and 33B are electric fields of an insulated and
non-insulated dynamic transmission line on a first day;
[0064] FIGS. 34A and 34B are temperature distributions of a
partially insulated dynamic transmission line after 1 and 20
days;
[0065] FIGS. 35A to 35F are schematic views of pipe configurations
that may be used in an apparatus for electromagnetic heating of
formations, according to one embodiment;
[0066] FIGS. 36 and 37 are schematic and perspective views of an
apparatus for electromagnetic heating of formations according to
another embodiment;
[0067] FIG. 38 is a schematic view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0068] FIG. 39 is a schematic view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0069] FIGS. 40A to 40H are cross-sectional views of the electric
fields of an apparatus for electromagnetic heating of formations
according to the embodiment shown in FIG. 39;
[0070] FIG. 41 is a schematic view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0071] FIG. 42 is a schematic view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0072] FIG. 43 is a schematic view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0073] FIG. 44 is a schematic view of another transmission line
conductor arrangements that may be used in an apparatus for
electromagnetic heating of formations, according to one
embodiment;
[0074] FIG. 45 is a profile view of an apparatus for
electromagnetic heating of formations according to another
embodiment;
[0075] FIG. 46 is a perspective view of a choke for an apparatus
for electromagnetic heating of formations according to the
embodiment shown in FIG. 45;
[0076] FIG. 47 is a profile view of an apparatus for
electromagnetic heating of formations according to another
embodiment; and
[0077] FIGS. 48A and 48B are methods for electromagnetic heating of
formations according to one embodiment.
[0078] The skilled person in the art will understand that the
drawings, described below, are for illustration purposes only. The
drawings are not intended to limit the scope of the applicants'
teachings in anyway. Also, it will be appreciated that for
simplicity and clarity of illustration, elements shown in the
figures have not necessarily been drawn to scale. For example, the
dimensions of some of the elements may be exaggerated relative to
other elements for clarity. Further, where considered appropriate,
reference numerals may be repeated among the figures to indicate
corresponding or analogous elements.
DESCRIPTION OF VARIOUS EMBODIMENTS
[0079] It will be appreciated that numerous specific details are
set forth in order to provide a thorough understanding of the
exemplary embodiments described herein. However, it will be
understood by those of ordinary skill in the art that the
embodiments described herein may be practiced without these
specific details. In other instances, well-known methods,
procedures and components have not been described in detail so as
not to obscure the embodiments described herein. Furthermore, this
description is not to be considered as limiting the scope of the
embodiments described herein in any way, but rather as merely
describing the implementation of the various embodiments described
herein.
[0080] It should be noted that terms of degree such as
"substantially", "about" and "approximately" when used herein mean
a reasonable amount of deviation of the modified term such that the
end result is not significantly changed. These terms of degree
should be construed as including a deviation of the modified term
if this deviation would not negate the meaning of the term it
modifies.
[0081] In addition, as used herein, the wording "and/or" is
intended to represent an inclusive-or. That is, "X and/or Y" is
intended to mean X or Y or both, for example. As a further example,
"X, Y, and/or Z" is intended to mean X or Y or Z or any combination
thereof.
[0082] It should be noted that the term "coupled" used herein
indicates that two elements can be directly coupled to one another
or coupled to one another through one or more intermediate
elements.
[0083] It should be noted that phase shifts or phase differences
between time-harmonic (e.g. a single frequency sinusoidal) signals
can also be expressed as a time delay. For time harmonic signals,
time delay and phase difference convey the same physical effect.
For example, a 180.degree. phase difference between two
time-harmonic signals of the same frequency can also be referred to
as a half-period delay. As a further example, a 90.degree. phase
difference can also be referred to as a quarter-period delay. Time
delay is typically a more general concept for comparing periodic
signals. For instance, if the periodic signals contain multiple
frequencies (e.g. a series of rectangular or triangular pulses),
then the time lag between two such signals having the same
fundamental harmonic is referred to as a time delay. For
simplicity, in the case of single frequency sinusoidal signals the
term "phase shift" shall be used. In the case of multi-frequency
periodic signals, the term "phase shift" shall refer to the time
delay equal to the corresponding time delay of the fundamental
harmonic of the two signals.
[0084] Referring to FIG. 1, there is a profile view of an apparatus
1 according to at least one embodiment. The apparatus 1 may be used
for electromagnetic heating of a hydrocarbon formation 100. The
apparatus 1 includes an electrical power source 10, an
electromagnetic (EM) wave generator 14, and two transmission line
conductors 20 and 22.
[0085] The electrical power source 10 generates electrical power.
The electrical power may be one of alternating current (AC) or
direct current (DC). Power cables 12 carry the electrical power
from the electrical power source 10 to the EM wave generator
14.
[0086] The EM wave generator 14 generates EM power. It will be
understood that EM power can be high frequency alternating current,
alternating voltage, current waves, or voltage waves. The EM power
can be a periodic high frequency signal having a fundamental
frequency (f.sub.0). The high frequency signal can have a
sinusoidal waveform, square waveform, or any other appropriate
shape. The high frequency signal can further include harmonics of
the fundamental frequency. For example, the high frequency signal
can include second harmonic 2f.sub.0, and third harmonic 3f.sub.0
of the fundamental frequency f.sub.0. In some embodiments, the EM
wave generator 14 can produce more than one frequency at a time. In
some embodiments, the frequency and shape of the high frequency
signal may change over time. The term "high frequency alternating
current", as used herein, broadly refers to a periodic, high
frequency EM power signal, which in some embodiments, can be a
voltage signal.
[0087] The frequency of the EM power may be lower than that used by
conventional RF antennas. In particular, the frequency of the EM
power generated by EM wave generator 14 may be between 1 kilohertz
(kHz) to 10 megahertz (MHz). Any appropriate frequency between 1
kHz to 10 MHz may be used. In some embodiments, the frequency of
the EM power generated by EM wave generator 14 may be between 1 kHz
to 1 MHz. In some embodiments, the frequency of the EM power
generated by EM wave generator 14 may be between 1 kHz to 200
kHz.
[0088] Use of lower frequency EM power provides more efficient and
cost effective options for EM wave generators. For example, low
frequency EM wave generators can be built utilizing Silicon Carbide
(SiC) transistors, which offer high power (e.g., approximately 100
kW to 300 kW per transistor or pair of transistors) and high
efficiency (e.g., approximately 98% efficiency). SiC transistors
cannot operate effectively in high frequency ranges in the order of
megahertz (MHz). Furthermore, SiC transistors can operate at high
temperatures (e.g., over 200.degree. C.). EM wave generator 14 can
include an inverter, a pulse synthesizer, a transformer, one or
more switches, a low-to-high frequency converter, an oscillator, an
amplifier, or any combination of one or more thereof.
[0089] The transmission line conductors 20 and 22 are coupled to
the EM wave generator 14. Each of the transmission line conductors
20 and 22 can be defined by a pipe. In some embodiments, the
apparatus may include more than two transmission line conductors.
In some embodiments, only one or none of the transmission line
conductors may be defined by a pipe. In some embodiments, the
transmission line conductors 20 and 22 may be conductor rods,
coiled tubing, or coaxial cables, or any other pipe to transmit EM
energy from EM wave generator 14.
[0090] In FIG. 1, each pipe is a pipe string of a conventional
steam-assisted gravity drainage (SAGD) system. Conventional SAGD
systems typically comprise a pair of pipe strings, that is, an
injector pipe and a producer pipe for conveying fluids. A producer
pipe typically conveys fluids from an underground formation to the
surface, or above ground. Meanwhile, an injector pipe typically
conveys fluids from the surface to an underground formation. A pair
of pipe strings is substantially horizontal (i.e., parallel to the
surface) (as shown in FIG. 1), When a pair of pipe strings are
substantially horizontal, the producer pipe is generally located at
a lower depth from the surface than the injector pipe. Under
circumstances in which there are more than one injector pipes, the
producer pipe can similarly be located a lower depth from the
surface than the injector pipes
[0091] In some embodiments, a pipe string of a conventional SAGD
system can be used as a transmission line conductor 20 and 22
without interfering with the use of the pipe string for conveying
fluids. That is, the interior cavity of the pipe string can remain
usable for conveying fluids.
[0092] The pipe can generally be a contiguous, metallic pipe.
Conventional SAGD pipe strings are typically carbon steel having
relatively low conductivity and high magnetic permeability.
However, the large diameter of SAGD pipe strings and low
operational frequency can provide sufficiently low electrical
resistivity such that little heat is generated on the pipe surface
at the frequency of the EM power. In some embodiments, highly
conductive metals having low magnetic permeability can be cladded
to the pipe strings. In some embodiments, no cladding is provided
and the metallic pipe is in direct contact with the hydrocarbon
formation. In some embodiments, the metallic pipe is partially or
fully covered with electrical insulation.
[0093] When the interior cavity of the pipe string remains usable
for conveying fluids, the transmission line conductors 20 and 22
are more specifically defined by the external surface of the pipe.
That is, the exterior surface of the pipe can be used for
transmitting high frequency current. In some embodiments,
transmission line conductors 20 and 22 only transmit EM energy from
EM wave generator 14 and do not convey fluids.
[0094] In some embodiments, one or more injector pipes and/or one
or more producer pipes from different pipe strings can be used as
transmission line conductors. For example, an injector pipe from a
first pipe string can be used as a first transmission line
conductor and a producer pipe from a second pipe string can be used
as a second transmission line conductor. Furthermore, an injector
pipe from the second pipe string can also be used as a third
transmission line conductor. In some other embodiments, two or more
injector pipes are used as transmission line conductors, while
producer pipes are not used as transmission line conductors. In
other words the producer pipes in this case are left just to
produce.
[0095] The transmission line conductors 20 and 22 are coupled to
the EM wave generator 14. The transmission line conductors 20 and
22 can have a proximal end and a distal end. The proximal end of
the transmission line conductors 20 and 22 can be coupled to the EM
wave generator 14. The transmission line conductors 20 and 22 can
be excited by the high frequency alternating current generated by
the EM wave generator 14. When excited, the transmission line
conductors 20 and 22 form an open transmission line between
transmission line conductors 20 and 22. The open transmission line
carries EM energy in a cross-section of a radius comparable to a
wavelength of the excitation. The open transmission line propagates
an electromagnetic wave from the proximal end of the transmission
line conductors 20 and 22 to the distal end of the transmission
line conductors 20 and 22. In some embodiments, the electromagnetic
wave may propagate as a standing wave. In other embodiments, the
electromagnetic wave may propagate as a partially standing wave. In
yet other embodiments, the electromagnetic wave may propagate as a
travelling wave.
[0096] The hydrocarbon formation between the transmission line
conductors 20 and 22 can act as a dielectric medium for the open
transmission line. The open transmission line can carry and
dissipate energy within the dielectric medium, that is, the
hydrocarbon formation. The open transmission line formed by
transmission line conductors and carrying EM energy within the
hydrocarbon formation may be considered a "dynamic transmission
line". By propagating an electromagnetic wave from the proximal end
of the transmission line conductors 20 and 22 to the distal end of
the transmission line conductors 20 and 22, the dynamic
transmission line may carry EM energy within long wells. Wells
spanning a length of 500 meters (m) to 1500 meters (m) can be
considered long wells.
[0097] The impedance of the dynamic transmission line may depend
weakly on frequency. In a lossy medium, the impedance will be
complex. However, the apparatus may be designed such that the real
value of complex impedance is significant. In some embodiments, the
real value of complex impedance may be designed to be between 1 Ohm
(.OMEGA.) and 1000 Ohms (.OMEGA.). In some embodiments, the real
value of complex impedance may be designed to be between 10 Ohms
(.OMEGA.) to 100 Ohms (.OMEGA.). In some embodiments, the real
value of complex impedance may be designed to be between 1 Ohm
(.OMEGA.) and 30 Ohms (.OMEGA.). The coupling of the EM wave
generator to the transmission line conductors is simplified when
the real value of complex impedance is significant.
[0098] As the hydrocarbon formation is heated, the characteristics
of the hydrocarbon formation, and in particular, the impedance,
change. To minimize the impact of such impedance changes, the
dynamic transmission line is operated at much lower frequencies
than that of conventional RF antennas. Operation of the dynamic
transmission line at lower frequencies further simplifies the
coupling of the EM wave generator to the transmission line
conductors.
[0099] In some embodiments, the dynamic transmission line may be
operated to achieve a temperature between 150.degree. C. to
250.degree. C. The dynamic transmission line can be operated to
achieve temperatures that result in steam generation. Depending on
the depth of and the pressure in the hydrocarbon formation, steam
generation can typically occur between 100.degree. C. and
300.degree. C.
[0100] Each of the transmission line conductors 20 and 22 can be
coupled to the EM wave generator 14 via a waveguide 24 and 26 for
carrying high frequency alternating current from the EM wave
generator 14 to the transmission line conductors 20 and 22. Each of
the waveguides 24 and 26 can have a proximal end and a distal end.
The proximal ends of the waveguides can be connected to the EM wave
generator 14. The distal ends of the waveguides 24 and 26 can be
connected to the transmission line conductors 20 and 22.
[0101] Waveguides 24 and 26 are shown in FIG. 1 as being
substantially vertical (i.e., perpendicular to the surface). In
some embodiments, one or both of waveguides 24 and 26, metal casing
pipe 28 and 30, or sections thereof can be angled or curved with
respect to the surface.
[0102] Each waveguide 24 and 26 can include a pipe and metal casing
pipe 28 and 30 concentrically surrounding the pipe. The pipe can
form an inner conductor and the metal casing pipe 28 and 30 can
form an outer conductor of the waveguide 24 and 26. Together, the
pipe and metal casing 28 and 30 form a two-conductor waveguide, or
coaxial transmission line. In some embodiments, the two-conductor
waveguide can be provided by a power cable or a coaxial
transmission line.
[0103] In some embodiments, an inner conductor can be provided by
at least one of a wire and a conductor rod. In FIG. 1, the inner
conductors of the waveguides are provided by the injector pipe and
the producer pipe of a conventional SAGD system. In particular, the
inner conductors are provided by the vertical portions of the
injector and producer pipes. Each inner conductor can be coupled to
the EM wave generator 14 via high frequency connectors 16 and 18.
The high frequency connectors 16 and 18 may pass through
conventional SAGD system infrastructure 48.
[0104] The two-conductor waveguide structure can further include a
dielectric layer 32 and 34 disposed between the pipe and metal
casing pipe 28 and 30 for electromagnetically isolating the pipe.
The dielectric layer 32 and 34 can fill the space between the pipe
and metal casing pipe 28 and 30. The dielectric layer 32 and 34 can
have a low loss at high frequencies. The dielectric layer can allow
for high efficiency power transfer at high frequencies.
[0105] In FIG. 1, the dielectric layer 32 and 34 is air. Any
appropriate dielectric layer 32 and 34 may be used. In some
embodiments, the dielectric layer 32 and 34 can be formed of a
solid dielectric material such as ceramics, structural ceramics,
polyether ether ketone (PEEK), or polytetrafluoroethylene (PTFE)
(i.e., Teflon.RTM.). In some embodiments, the dielectric layer 32
and 34 can include at least one dielectric centralizer. In some
embodiments, the dielectric layer can be formed of a fluid, such as
pressurized gas.
[0106] The dielectric layer 32 and 34 can have a dielectric
constant between 1 to 100. Any appropriate dielectric layer 32 and
34 having a dielectric constant between 1 to 100 may be used. In
some embodiments, a dielectric layer 32 and 34 having a dielectric
constant between 1 to 25 can be used. In some embodiments, a
dielectric layer 32 and 34 having a dielectric constant between 1
to 4 can be used. In some embodiments, dielectric layer 32 and 34
can have a high dielectric breakdown voltage to allow the
two-conductor waveguide structure to operate at higher voltages,
thus increasing the power capacity of the waveguide.
[0107] The outer conductors of the waveguides can be electrically
grounded at 42 and 44 to block a substantial portion of high
frequency alternating current from travelling along the exterior
surfaces of the waveguides 24 and 26, and in particular, the outer
conductors 28 and 30. High frequency alternating current travelling
along the exterior surfaces of the waveguides 28 and 30 may travel
in a direction that is different from the direction of the
electromagnetic wave propagating along the transmission line
conductors 20 and 22. That is, high frequency alternating current
travelling along the exterior surfaces of the waveguides 28 and 30
may travel in a direction away from the transmission line
conductors 20 and 22 and return to the surface, or above
ground.
[0108] The EM wave generator 14 and the metal casing pipes 28 and
30 of the waveguides 24 and 26 can be electrically grounded to a
common ground 40, 42, and 44. As shown in FIG. 1, an optional
electrical short 46 between the metal casing pipes 28 and 30 may be
used to electrically ground the metal casing pipes 28 and 30 to a
common ground.
[0109] At least part of a length of the outer conductors of the
waveguides can be concentrically surrounded by a separation medium
36 and 38 for electrically isolating the outer conductors 28 and 30
and preserving the structural integrity of the borehole. In FIG. 1,
the separation medium 36 and 38 is formed of cement.
[0110] Each of the high frequency connectors 16 and 18 carry high
frequency alternating current from the EM wave generator 14 to the
inner conductors. In some embodiments, the high frequency
alternating current being transmitted to the first waveguide 24 via
high frequency connector 16 is substantially identical to the high
frequency alternating current being transmitted to the second
waveguide 26 via high frequency connector 18. The expression
substantially identical is considered here to mean sharing the same
waveform shape, frequency, amplitude, and being synchronized. In
some embodiments, the high frequency alternating current being
transmitted to the first waveguide 24 via high frequency connector
16 is a phase-shifted version of the high frequency alternating
current being transmitted to the second waveguide 26 via high
frequency connector 18. The expression phase-shifted version is
considered here to mean sharing the same waveform, shape,
frequency, and amplitude but not being synchronized. In some
embodiments, the phase-shift may be a 180.degree. phase shift. In
some embodiments, the phase-shift may be an arbitrary phase shift
so as to produce an arbitrary phase difference.
[0111] As shown in FIG. 1, the EM wave generator 14 is located
above ground, or at the surface. In some embodiments, the EM wave
generator may be located underground. An apparatus with the EM wave
generator located above ground rather than underground may be
easier to deploy. However, when the EM wave generator is located
underground, transmission losses are reduced because EM energy is
not dissipated in the areas that do not produce hydrocarbons (i.e.,
distance between the EM wave generator and the transmission line
conductors). When the EM wave generator is located above ground,
transmission losses between the EM wave generator and the
transmission line conductors may be reduced by positioning such
vertical pipe sections close together and filling the space with
low loss materials to reduce power loss.
[0112] An apparatus with the EM wave generator located above ground
may also be used for SAGD preheating applications. That is, EM
energy may be used to temporarily preheat areas between the
injector and producer to increase the hydraulic communication
between the wells before the onset of steam flooding. SAGD
preheating can significantly accelerate production out of a new
SAGD pair.
[0113] Referring to FIG. 2, there is a profile view of an apparatus
2 according to at least one example embodiment. Features common to
apparatus 1 and 2 are shown using the same reference numbers. In
apparatus 2, a high frequency connector 18 carries high frequency
alternating current from the EM wave generator 14 to the inner
conductor of a second waveguide 26. The EM wave generator 14, the
outer conductor 30 of the second waveguide 26, and the inner
conductor of the first waveguide 24 are connected to a common
ground 40, 44, and 52. The outer conductor 28 of the first
waveguide 24 is also electrically grounded at 54. However,
electrical grounding 54 of the outer conductor 28 of the first
waveguide 24 is achieved separately from grounding through the
common ground 40, 44, and 52 to avoid short-circuiting the
transmission line conductor 20. As shown in FIG. 2, an optional
electrical short 50 may be provided between the metal casing pipe
30 and the inner conductor of the first waveguide 24.
[0114] Referring to FIG. 3, there is a profile view of an apparatus
3 according to at least one example embodiment. Features common to
apparatus 1, 2 and 3 are shown using the same reference numbers. In
apparatus 3, a high frequency connector 18 carries high frequency
alternating current from the EM wave generator 14 to the inner
conductor of a second waveguide 26. The EM wave generator 14 and
the inner conductor of the first waveguide 24 are connected to a
common ground 40 and 52. The outer conductors 28 and 30 of the
first and second waveguides 24 and 26 are also electrically
grounded at 54 and 56. However, electrical grounding of the outer
conductors 28 and 30 at 54 and 56 is achieved separately from
grounding through the electrical ground 40 and 52 to avoid
short-circuiting the transmission line conductors 20 and 22.
[0115] Referring to FIG. 4, there is a profile view of an apparatus
4 according to at least one example embodiment. The apparatus 4
includes an electrical power source 10, EM wave generators 72 and
74, and two transmission line conductors 20 and 22. Power cables 12
carry the electrical power from the electrical power source 10 to
the EM wave generators 72 and 74. Power cables 12 can be routed
through the pipes to connect to the EM wave generators 72 and 74.
In some embodiments, power cables 12 can be routed along the
outside of the pipes (not shown), or along conduits (not
shown).
[0116] As shown in FIG. 4, the EM wave generators 72 and 74 may be
located underground and disposed along the pipes. Each of the EM
wave generators 72 and 74 can include an inverter, a pulse
synthesizer, a transformer, one or more switches, a low-to-high
frequency converter, an oscillator, an amplifier, or any
combination of one or more thereof. In some embodiments, chokes 60
and 62 may be located at the surface and disposed along power cable
12 to block high frequency alternating current from returning to
the surface. In some embodiments, additional chokes 64 and 66 may
be located underground. Chokes 60, 62, 64, and 66 may be
implemented using any appropriate technique known to those skilled
in the art.
[0117] In some embodiments, chokes are not used at all. An
apparatus without chokes can allow for simpler deployment.
Furthermore, chokes can be lossy and the elimination of chokes can
increase the power efficiency of the apparatus. As well, chokes can
be frequency dependent. That is, chokes can have a limited
operational frequency range. The operational frequency range of
chokes can in turn limit the selection of the frequency of EM power
generated by the EM wave generators 72 and 74. Hence, the
elimination of chokes can allow for a greater range of EM power to
be used. In some embodiments, the pipes upstream of the EM wave
generators 72 and 74 can be electrically grounded at 68 and 70 to
prevent or limit high frequency alternating current from returning
to the surface, as shown in FIG. 4.
[0118] The EM wave generators 72 and 74 generate the high frequency
alternating current. Each of the EM wave generators 72 and 74 can
be connected through a common ground. In some embodiments, the high
frequency alternating current generated by EM wave generator 72 is
substantially identical to the high frequency alternating current
generated by EM wave generator 74. In some embodiments, the high
frequency alternating current generated by EM wave generator 72 is
a phase-shifted version of the high frequency alternating current
generated by EM wave generator 74. For example, the high frequency
alternating current generated by EM wave generator 72 can be a
sinusoidal signal and the high frequency alternating current
generated by EM wave generator 74 can be a 180.degree.
phase-shifted version of the sinusoidal signal generated by EM wave
generator 72. Alternatively, the high frequency alternating current
generated by EM wave generator 74 can be a phase-shifted version of
the sinusoidal EM wave generated by EM wave generator 72 in which
the phase shift is an arbitrary phase shift.
[0119] Each of the high frequency connectors 76 and 78 carry high
frequency alternating current from the EM wave generators 72 and 74
to transmission line conductors 20 and 22. In this embodiment, the
high frequency connectors 76 and 78 can be a power cable. Each of
the high frequency connectors 76 and 78 provide a first conductor
of the two-conductor waveguide. The electrical grounding of the EM
wave generators 72 and 74 provide a second conductor of the
two-conductor waveguide.
[0120] Each of the high frequency connectors 76 and 78 can have a
proximal end and a distal end. The proximal ends of the high
frequency connectors can be connected to the EM wave generators 72
and 74. The distal ends of the high frequency connectors can be
connected one of the transmission line conductors 20 and 22.
[0121] To connect the distal ends of the high frequency connectors
76 and 78 to the exterior surface of pipes, a lengthwise segment of
the pipes can be removed to form a pipe opening. In some
embodiments, the high frequency connectors 76 and 78 are positioned
to contact the exterior surface of the pipes. In some embodiments,
the high frequency connectors 76 and 78 may pass through the pipe
opening in order to contact the exterior surface of the pipe.
[0122] Insulating material 80 and 82 can be provided to plug the
pipe opening. Insulating material 80 and 82 can block substances
from entering the pipes. More specifically, insulating material 80
and 82 can block solids, liquids, and gases from the hydrocarbon
formation surrounding the pipe opening from entering pipes via the
pipe opening. Insulating material 80 and 82 can be inert, or not
chemically reactive, to such solids, liquids and gases from the
hydrocarbon formation. If insulating material is chemically
reactive to solids, liquids and gases from the hydrocarbon
formation, the insulating material may disintegrate over time.
Insulating material 80 and 82 can also provide structural
continuity and integrity for pipes. Insulating material 80 and 82
can be mechanically strong enough to withstand pressure within
pipes from pushing into the hydrocarbon formation.
[0123] Insulating material 80 and 82 can have a low dissipation
factor (tan .delta.) to reduce electrical losses at the frequency
of operation. In particular, any appropriate insulating material
having dissipation factor less than 0.01 may be used. In some
embodiments, the insulating material may have a dissipation factor
less than 0.005. Insulating material 80 and 82 may be exposed to
high temperatures. Any appropriate insulating material 80 and 82
capable of withstanding temperatures greater than 250.degree. C.
may be used. Insulating material 80 and 82 can be any appropriate
dielectric material. For example, insulating material can include
ceramics, synthetic polymers, plastics, and less preferably,
fiberglass and cement, or a combination thereof. The properties of
insulating material 80 and 82 are less stringent than the
properties required for providing an electrically lossless material
around dipole arms of conventional RF antennas.
[0124] Referring to FIG. 5, there is a profile view of an apparatus
5 according to at least one example embodiment. Features common to
apparatus 4 and 5 are shown using the same reference numbers. In
contrast to apparatus 4 which includes two EM wave generators 72
and 74, apparatus 5 includes only one EM wave generator 74 disposed
along the pipe. A first high frequency connector 78 carries high
frequency alternating current from the EM wave generator 74 to
transmission line conductor 22 and a second high frequency
connector 84 carries high frequency alternating current from the EM
wave generator 74 to transmission line conductor 20. Although
apparatus 5 does not include an EM wave generator disposed along
the second pipe, insulating material 80 can be provided along the
second pipe to electrically isolate the transmission line conductor
20 from the vertical portion of the second pipe.
[0125] In some embodiments, an electrical short 86 between the
pipes upstream of, or prior to pipe openings can be provided to
block high frequency alternating current from returning above
ground, or to the surface. More specifically, electrical short 86
blocks high frequency alternating current from flowing on the
external surface of the vertical portion of pipes. In some
embodiments, an electrical short 88 between pipes at the distal end
of the transmission line conductors 20 and 22 can be provided to
adjust the impedance seen by the EM wave generator 74.
[0126] Referring to FIG. 6, there is a profile view of an apparatus
6 according to at least one example embodiment. Features common to
apparatus 4, 5, and 6 are shown using the same reference numbers.
Similar to apparatus 4, apparatus 6 includes two EM wave generators
90 and 92. However, in contrast to the EM wave generators 72 and 74
which are disposed along the pipe and located underground, the EM
wave generators 90 and 92 are located above ground, at the surface.
Each of the EM wave generators 90 and 92 can include an inverter, a
pulse synthesizer, a transformer, one or more switches, a
low-to-high frequency converter, an oscillator, an amplifier, or
any combination of one or more thereof.
[0127] A first high frequency connector 94 carries high frequency
alternating current from the EM wave generator 90 to transmission
line conductor 20 and a second high frequency connector 96 carries
high frequency alternating current from the EM wave generator 92 to
transmission line conductor 22. Although apparatus 6 does not
include an EM wave generators disposed along the pipes, insulating
material 80 and 82 are provided along the pipes to electrically
isolate the transmission line conductors 20 and 22 from waveguides
102 and 104.
[0128] Each of the transmission line conductors 20 and 22 can be
coupled to the EM wave generator 14 via waveguide 102 and 104 for
carrying high frequency alternating current from the EM wave
generators 90 and 92 to the transmission line conductors 20 and 22.
Each of the waveguides 102 and 104 can have a proximal end and a
distal end. The proximal ends of the waveguides can be connected to
the EM wave generators 90 and 92. The distal ends of the waveguides
can be connected one of the transmission line conductors 20 and
22.
[0129] Each waveguide 102 and 104 can include a pipe and high
frequency connector 94 and 96 located within the pipe. The pipe can
form an outer conductor and the high frequency connectors 94 and 96
can form the inner conductors of the waveguides 102 and 104.
Together, the pipe and high frequency connector 94 and 96 form a
two-conductor waveguide, or coaxial transmission line.
[0130] Referring to FIG. 7, there is a profile view of an apparatus
7 according to at least one example embodiment. Features common to
apparatus 1, 6 and 7 are shown using the same reference numbers.
Similar to apparatus 1, apparatus 7 includes an EM wave generator
14 located above ground, at the surface. Similar to apparatus 6,
apparatus 7 includes two-conductor waveguides 102 and 104 formed by
pipes and high frequency connectors 16 and 18 located within the
pipes. The pipes can form an outer conductor and the high frequency
connectors 16 and 18 can form an inner conductor of waveguides 102
and 104 as shown.
[0131] Referring to FIG. 8, there is a profile view of an apparatus
8 according to at least one example embodiment. Features common to
apparatus 5, 6 and 8 are shown using the same reference numbers. In
contrast to apparatus 6, which includes two EM wave generators 90
and 92, apparatus 8 includes only one EM wave generator 92.
[0132] A high frequency connector 96 carries high frequency
alternating current from the EM wave generator 92 to transmission
line conductor 22. Although the EM wave generator 92 is located
above ground and not disposed along the pipe, insulating material
82 can be provided along the pipe to electrically isolate
transmission line conductor 22 from the two-conductor waveguide
104. The two-conductor waveguide 104 includes the high frequency
connector 96 located within the pipe. The high frequency connector
96 provides an inner conductor for waveguide 104 and the pipe
provides an outer conductor for waveguide 104. The second pipe, or
transmission line conductor 20, and the EM wave generator 92 are
electrically grounded to a common ground at 68 and 79 to form the
dynamic transmission line.
[0133] Similar to apparatus 5, an electrical short 86 is provided
between the pipes upstream of, or prior to, pipe opening 82 and
transmission line conductors 20 and 22 to block high frequency
alternating current from returning above ground, or to the surface.
More specifically, electrical short 86 blocks high frequency
alternating current from flowing on the external surface of the
vertical portion of pipes.
[0134] Referring to FIG. 9, there is a profile view of an apparatus
9 according to at least one example embodiment. Features common to
apparatus 5 and 9 are shown using the same reference numbers.
Similar to apparatus 5, apparatus 9 includes only one EM wave
generator 108 located underground. However, as shown, EM wave
generator 108 of apparatus 9 is located further along the pipe
string. EM wave generator 108 can include an inverter, a pulse
synthesizer, a transformer, one or more switches, a low-to-high
frequency converter, an oscillator, an amplifier, or any
combination of one or more thereof. Similar to insulating material
80 and 82, insulating material 114 can be provided to plug the pipe
opening.
[0135] In this example embodiment, transmission line conductor 22
is split into two portions: a first portion 22a located between
insulating materials 82 and 114, and a second portion 22b located
after insulating material 114; that is, between insulating material
114 and the distal end of transmission line conductor 22. A first
high frequency connector 110 can be used as the waveguide for
carrying high frequency alternating current from the EM wave
generator 108 to transmission line conductor 22a. A second high
frequency connector 112 can also be used as the waveguide for
carrying high frequency alternating current from the EM wave
generator 108 to transmission line conductor 22b.
[0136] Similar to apparatus 8, apparatus 9 can include choke 66
disposed along the pipe to block high frequency alternating current
from returning above ground. Apparatus 9 can also include
additional choke 106 located further along the pipe string, namely,
within transmission line conductor 22a. As shown in FIG. 9, an
electrical short 88 between pipes at the distal end of the
transmission line conductors 20 and 22 can be provided to adjust
the impedance seen by the EM wave generator 108. Electrical short
88 can also delineate a limit to the active portion of the
transmission line conductors 20 and 22. That is, electrical short
88 can delineate the portion of the transmission line conductors 20
and 22 that delivers EM energy to the hydrocarbon formation.
[0137] In the example embodiment shown in FIG. 9, the apparatus 9
can simultaneously operate as an open transmission line and an
antenna. That is, apparatus 9 has a similar structure to a folded
dipole. However, in contrast to conventional folded dipoles,
apparatus 9 is located in a lossy medium and therefore the resonant
nature of the dipole is not required. Furthermore, the impedance
transforming capacity of apparatus 9 may be reduced with the
provision of an additional electrical short 88 at the distal end of
the transmission line conductors.
[0138] Referring to FIG. 10, there is a profile view of an
apparatus 11 according to at least one example embodiment. Features
common to apparatus 8, 9 and 11 are shown using the same reference
numbers. Similar to apparatus 8, apparatus 10 includes only one EM
wave generator 92 located above ground, or at the surface. Similar
to apparatus 9, transmission line conductor 22 is split into two
portions: a first portion 22a located between insulating materials
82 and 114, and a second portion 22b located after insulating
material 114; that is, between insulating material 114 and the
distal end of transmission line conductor 22. A first high
frequency connector 110 can be used as a waveguide for carrying
high frequency alternating current from the EM wave generator 92 to
transmission line conductor 22a and a second high frequency
connector 112 can be used as a waveguide for carrying high
frequency alternating current from the EM wave generator 92 to
transmission line conductor 22b.
[0139] Referring to FIGS. 11A to 11D, there is cross-sectional
views of transmission line conductors 20 and 22 and outer waveguide
conductors according to at least one example embodiment.
Transmission line conductors 20 and 22 and outer waveguide
conductors can be formed of a plurality of pipe sections. FIG. 11A
illustrates a single pipe section 200. Each pipe section can
include connecting ends. The connecting ends may provide a female
member 206 or a male member 208. The female member 206 and male
member 208 can be mateable with a corresponding male member 208 or
female member 206 of another pipe section respectively. The
connecting ends are not limited to threaded pipe sections. In some
embodiments, the connecting ends may include clamps, other
fastening means, or a combination of fastening means. As shown in
FIG. 11B, multiple pipe sections can be connected together into a
multiple pipe sections 210.
[0140] In some embodiments, pipe sections can be electrically
insulated by providing electrical insulation 204 adjacent to, or
covering the metallic pipe section 202. In some embodiments, pipe
sections can be partially insulated as in the case of pipe section
200 shown in FIG. 11A or completely insulated as in the case of the
pipe section 212 in FIG. 11C. As shown by the multiple pipe
sections 210 of FIG. 11B, when pipe sections are partially
insulated and connected together, portions of metallic pipe
sections remain exposed. When installed in an underground
reservoir, the exposed metallic pipe sections may come in direct
contact with the hydrocarbon formation. Partially insulated pipe
sections such as pipe sections 210 shown in FIG. 11B can be easier
to assemble, particularly at rigs.
[0141] As shown in FIG. 11D, when pipe sections are completely
insulated and connected together in multiple pipe sections 216, the
metallic pipe sections are not exposed. With completely insulated
pipe sections 212, a seal 214 can be provided at the connecting end
to insulate the junction between female members 206 and male
members 208. The seal 214 may be formed of any high temperature,
oil and gas compatible insulating material. For example, the seal
214 may be Vitron.RTM. O-rings.
[0142] Any appropriate electrical insulation 204 may be used. In
some embodiments, the electrical insulation 204 may be insulating,
high temperature paint. Examples of insulating, high temperature
paint include aluminum oxide, or titanium oxide filled enamel
paints, or ceramic paints. In some embodiments, the electrical
insulation 204 may be a dielectric material.
[0143] Referring to FIGS. 12A and 12B, there are cross-sectional
views of transmission line conductors 20 and 22 according to at
least one example embodiment. In some embodiments, additional
layers 218 of electrical insulation may be provided (shown in FIGS.
12A and 12B). Additional layers 218 may be provided over top of the
electrical insulation 204, particularly when the electrical
insulation 204 covering the metallic pipe 200 is mechanically
fragile. Additional layers 218 may be designed to be sacrificial.
That is, additional layers 218 may be provided to protect the
electrical insulation layer 204 during deployment. Additional
layers 218 may be designed to be destroyed during deployment, or at
the onset of heat exposure. Any appropriate material may be used to
provide additional layers 218. For example, additional layers 218
can be a powder coating based on epoxy.
[0144] As shown in FIG. 12B, in some embodiments, cladding 220 may
be provided between the electrical insulation 204 and metallic pipe
200 to improve the electrical conductivity of metallic pipe 200 and
to provide better adhesion of the electrical insulation 204 to the
metallic pipe 200. Cladding 220 may be highly conductive metal with
low magnetic permeability. Any appropriate material may be used to
provide cladding 220. For example, cladding 220 may be copper or
aluminum. If aluminum cladding is used, the aluminum can be
anodized. Any appropriate anodizing process may be used. For
example, plasma anodizing can be used to eliminate pores in the
metallic pipe. Alternatively, less sophisticated anodizing
processes may be followed by pore elimination processes. Cladding
220 may cover an entire pipe section or a portion of a pipe
section.
[0145] Referring to FIG. 13, there is a schematic top view of an
apparatus having five transmission line conductor pairs and one EM
wave generator 14. Although only one EM wave generator 14 is shown,
in some embodiments, a plurality of EM wave generators may be used.
Since conventional SAGD systems typically include well pairs of
injector and producer pipes, such well pairs may be utilized to
provide an open transmission line. That is, each well pair can
provide a pair of transmission line conductors for one open
transmission line. Each of the transmission line conductor pairs is
excitable by the high frequency alternating current in one of the
manners described above. Additionally, phase shifts can be provided
for high frequency alternating current provided to neighboring well
pairs. More specifically, the high frequency alternating current
provided to producer pipe 20 of well pair 20 and 22 can be
180.degree. out of phase from the high frequency alternating
current provided to producer pipe 420 of well pair 420 and 422. As
well, the high frequency alternating current provided to injector
pipe 22 of well pair 20 and 22 can be 180.degree. out of phase from
the high frequency alternating current provided to injector pipe
422 of well pair 420 and 422. Furthermore, the high frequency
alternating current provided to producer pipe 420 of well pair 420
and 422 can be 180.degree. out of phase from the high frequency
alternating current provided to producer pipe 520 of well pair 520
and 522. In this way, additional transmission line pairs between
the neighboring producer pipes (20 and 420; 420 and 520; 520 and
620; 620 and 720) and between the neighboring injector pipes (22
and 422; 422 and 522; 522 and 622; 622 and 722) are formed,
enhancing the heating process and production efficiency. It should
be understood that, in some embodiments, phase shifts other than
180.degree. can also be used.
[0146] In addition to pipe strings of a well pair, additional
transmission line conductors (not shown in FIG. 13) can be provided
by conductor rods, pipes or wires to further enhance hydrocarbon
recovery. Additional transmission line conductors can be perforated
tubings that can supply fluid to the hydrocarbon formation. The
fluids can, for example, comprise steam or gas such as methane
(CH.sub.4), carbon dioxide (CO.sub.2). Carbon dioxide can be
supplied for CO.sub.2 sequestration in the hydrocarbon formation
after hydrocarbon production.
[0147] Referring to FIGS. 14 and 15, there is a profile view and a
cross-sectional view of an apparatus 13 according to at least one
example embodiment. Features common to apparatus 11 and 13 are
shown using the same reference numbers. Similar to apparatus 11,
apparatus 13 includes only one EM wave generator 92 located above
ground, or at the surface. While apparatus 13 is shown as having
one EM wave generator 92 located above ground, it will be
understood that in some embodiments, apparatus 13 can have two EM
wave generators 90 and 92, similar to apparatus 6.
[0148] Also similar to apparatus 9, a first high frequency
connector 110 can be used as a waveguide for carrying high
frequency alternating current from the EM wave generator 92 to
transmission line conductor 224 and a second high frequency
connector 112 can be used as a waveguide for carrying high
frequency alternating current from the EM wave generator 92 to
transmission line conductor 226. However, high frequency connectors
110 and 112 are not located within pipes 20 and 22. Each of pipes
20 and 22 are grounded at 68 and 70.
[0149] High frequency connectors 110 and 112 and transmission line
conductors 224 and 226 can be conductors or cables formed by coiled
tubing, other pipe strings, or a plurality of pipe sections as
shown in FIGS. 11A to 12B. As shown in FIG. 14, when conductors or
cable are used, the high frequency connectors 110 and 112 may be in
direct contact with the hydrocarbon formation. While high frequency
connectors 110 and 112 are shown in FIG. 14 as being substantially
vertical (i.e., perpendicular to the surface), it will be
understood that in some embodiments, any one or both of high
frequency connectors 110 and 112 or sections thereof can be angled
or curved with respect to the surface.
[0150] Alternatively, metal casings 166 and 168 may be provided to
form non-radiating coaxial transmission lines and to prevent direct
contact between the high frequency connectors 110 and 112 and the
hydrocarbon formation along the vertical portion of the high
frequency connectors 110 and 112. When metal casings 166 and 168
are used, the high frequency connectors 110 and 112 may be routed
through the metal casings 166 and 168. Each metal casing 166 and
168 can be electrically grounded 116 and 118 to prevent or limit
high frequency alternating current from returning to the surface
along the outer surface of metal casings 166 and 168. In some
embodiments, a choke can be provided at the distal end of each of
the metal casings 166 and 168 to prevent or limit high frequency
alternating current from returning to the surface along the outer
surface of the metal casings 166 and 168. In some embodiments,
metal casings 166 and 168 may be physically and electrically
connected to prevent high frequency alternating current from
returning to the surface along the outer surface of the casings
(shown as casings 160 and 162 in FIG. 25B). In some embodiments,
both high frequency connectors 110 and 112 may be routed through a
single metal casing (shown in FIG. 24B). In some other embodiments,
the single metal casings can be the result of casings 166 and 168
being welded together. In yet other embodiments, casings 166 and
168 can be welded together over a substantial portion of its
length. In some cases in which the casings 166 and 168 is welded
over a substantial portion of its length, the portion of the
casings 166 and 168 not attached may be located at distal ends. In
yet other embodiments, an electrical contact may be made between
casings 166 and 168 by inserting into the casings 166 and 168 into
a pipe of an appropriate size to provide sufficient force to
squeeze the two casings together. In some cases, the pipe may
further be provisioned to enhance electrical contact via inclusion
of additional welded wedges or contact points inside the pipe.
[0151] As shown in FIG. 15, when other pipe strings are used, high
frequency connectors 110 and 112 and transmission line conductors
224 and 226 can have a smaller diameter than typical of SAGD pipes
20 and 22. Using a smaller diameter can reduce drilling,
development, and material costs. The location of the transmission
line conductors 224 and 226 can be anywhere with respect to the
pipes 20 and 22. That is, the transmission line conductor 224 can
be located below, above, or in-between pipes 20 and 22.
[0152] In the example shown in FIG. 14, transmission line
conductors 224 and 226 are located above pipes 20 and 22. In the
example shown in FIG. 15, pipes 20 and 22 may be located above one
another and transmission line conductors 224 and 226 can be located
on either side of the pipes 20 and 22. The distance between the
transmission line conductors 224 and 226 can be any practical
distance that permits operation of the dynamic transmission line.
In some embodiments, the distance between the transmission line
conductors 224 and 226 is in the range of about 1 meter to about 20
meters.
[0153] Referring to FIGS. 16 and 17, there is a profile view and a
cross-sectional view of an apparatus 15 according to at least one
example embodiment. Features common to apparatus 13 and 15 are
shown using the same reference numbers. Similar to apparatus 13,
apparatus 15 includes only one EM wave generator 92 located above
ground, or at the surface. While apparatus 15 is shown as having
one EM wave generator 92 located above ground, it will be
understood that in some embodiments, apparatus 15 can have two EM
wave generators 90 and 92, similar to apparatus 6.
[0154] Also similar to apparatus 9, high frequency connectors 110
and 112 can be used as waveguides for carrying high frequency
alternating current from the EM wave generator 92 to transmission
line conductors 224 and 226. As well, the high frequency connectors
110 and 112 are not located within pipe 20. While high frequency
connectors 110 and 112 are respectively shown as being angled and
curved in FIG. 16, it will be understood that in some embodiments,
any one or both of high frequency connectors 110 and 112, or
sections thereof, can be substantially vertical, angled, or
curved.
[0155] It will be understood that where only two transmission line
conductors are described in this description as forming a dynamic
transmission line, any number of additional transmission line
conductors can be added. As shown in FIGS. 16 and 17, one of the
pipe strings of the SAGD well pair can be used to provide a third
transmission line conductor with appropriate excitation. For
example, pipe 20 may be electrically grounded at 68 to a common
ground 40 with the EM wave generator 92. Both pipe strings of the
SAGD well pair are not required. While FIGS. 16 and 17 show a third
transmission line conductor being provided by the producer pipe 20,
in other embodiments, a third transmission line conductor can be
provided by the injector pipe 22.
[0156] In some embodiments, it is preferable to provide a third
transmission line conductor 20 using the producer pipe of a SAGD
well pair, which carries oil from production. The injector pipe,
which normally provides steam to the SAGD system, is no longer
required as the hydrocarbon formation can be heated using EM
heating. The location of the transmission line conductors 224 and
226 can be above or parallel to pipe 20. In the example shown in
FIG. 16, transmission line conductors 224 and 226 are located above
pipe 20. In the example shown in FIG. 17, transmission line
conductors 224 and 226 can be located on either side of pipe
20.
[0157] As illustrated in FIG. 17, in some embodiments, metal
casings 168 and 166 can be physically separated. Each metal casing
166 and 168 can be electrically grounded 116 and 118 to prevent or
limit high frequency alternating current from returning to the
surface along the outer surface of casings 168 and 166. In some
embodiments, a choke can be provided at the distal end of each
metal casing 166 and 168 to prevent or limit high frequency
alternating current from returning to the surface along the outer
surface of the metal casings 166 and 168. In some embodiments, the
metal casings 168 and 166 can be physically and electrically
connected to prevent high frequency alternating current from
returning to the surface along the outer surface of the casings
(shown as casings 162 and 160 of FIG. 25B).
[0158] Referring to FIGS. 18 and 19, there is a profile view and a
cross-sectional view of an apparatus 17 according to at least one
example embodiment. Features common to apparatus 13 and 17 are
shown using the same reference numbers. Similar to apparatus 13,
apparatus 17 includes only one EM wave generator 92 located above
ground, or at the surface. A high frequency connector 110 can be
used as a waveguide for carrying high frequency alternating current
from the EM wave generator 92 to transmission line conductor 224.
As well, the high frequency connector 110 is not located within
pipe 20. While high frequency connector 110 is shown in FIG. 18 as
being substantially vertical (i.e., perpendicular to the surface),
it will be understood that in some embodiments, high frequency
connector 110, or sections thereof, can be angled or curved with
respect to the surface.
[0159] One of the pipe strings of the SAGD well pair can be used to
provide a second transmission line conductor with appropriate
excitation. For example, pipe 20 may be electrically grounded at 68
to a common ground 40 with the EM wave generator 92. Similar to
apparatus 15, apparatus 17 does not require both pipe strings of
the SAGD well pair. The standard SAGD injector pipe can be omitted
from apparatus 15 and heating of the hydrocarbon formation may be
provided by EM heating using apparatus 15 which only includes a
producer pipe. The location of the transmission line conductors 224
is typically above pipe 20, as shown in FIGS. 18 and 19. In the
example shown in FIG. 19, transmission line conductor 224 can be
located adjacent to pipe 20.
[0160] Referring to FIGS. 20 and 21, there is a profile view and a
cross-sectional view of an apparatus 21 according to at least one
example embodiment. Features common to apparatus 11 and 13 are
shown using the same reference numbers. Similar to apparatus 13,
apparatus 21 includes only one EM wave generator 92 located above
ground, or at the surface. While apparatus 21 is shown as having
one EM wave generator 92 located above ground, it will be
understood that in some embodiments, apparatus 21 can have two EM
wave generators 90 and 92, similar to apparatus 6.
[0161] Also similar to apparatus 13, a first high frequency
connector 110 can be used as a waveguide for carrying high
frequency alternating current from the EM wave generator 92 to
transmission line conductor 224 and a second high frequency
connector 112 can be used as a waveguide for carrying high
frequency alternating current from the EM wave generator 92 to
transmission line conductor 226. While high frequency connectors
110 and 112 are shown in FIG. 20 as being substantially vertical
(i.e., perpendicular to the surface), it will be understood that in
some embodiments, any one or both of high frequency connectors 110
and 112, or sections thereof, can be angled or curved with respect
to the surface.
[0162] As shown in FIG. 20, vertical pipes 150, 152, 154, and 156
can be used instead of horizontal pipes 20 and 22 for conveying
fluids, namely bitumen and heavy oil that have been mobilized by
the application of heat. A pump jack 140, 142, 144, and 146 can be
provided at each vertical pipe 150, 152, 154, and 156 to lift
liquid out of the well.
[0163] Vertical pipes may be used for, but is not limited to,
mine-face accessible hydrocarbon formations, formations that are
too deep for mining but too shallow for steam operations such as
SAGD or cyclic steam stimulation (CSS), or formations that are
partially depleted and in need of further simulation. Mine-face
accessible hydrocarbon formations can have a sloping mine wall that
is difficult to deplete using SAGD. Furthermore, mine-face
accessible hydrocarbon formations may not have the appropriate
geology, such as cap rock to allow for the steam injection.
Formations may be partially depleted because of limitations in
technology at the time oil was initially extracted from the
hydrocarbon formation.
[0164] In some embodiments, existing vertical pipes can be used
without further modification. Alternatively, vertical pipes can be
deployed along the length of formation 100. In some embodiments,
the vertical pipes can have an electrical ground 68.
[0165] In the example shown in FIG. 21, vertical pipes do not need
to be aligned along a single axis (i.e., a straight line). The
transmission line conductors 224 and 226 are located symmetrically
on either side of vertical pipe 150 but only on one side (i.e.,
offset) of vertical pipes 152 and 154. When transmission line
conductors are offset from the vertical pipes 152 and 154, a common
electrical ground for the vertical pipe 68 and the transmission
line conductors 116 and 118 may be required.
[0166] The vertical pipes can be located at any distance from the
transmission line conductors 224 and 226 that is practical for the
hydrocarbon formation 100 to be heated by the interaction with the
electromagnetic field. In some embodiments, the vertical pipes can
be located within about 100 meters from at least one of the
transmission line conductors 224 and 226. When the vertical pipes
are located at a far distance from the transmission line conductors
224 and 226, the heating process takes more time. Preferably, the
vertical pipes can be located within about 30 meters from at least
one of the transmission line conductors 224 and 226. Further
preferably, the vertical pipes can be located within about 5 to 20
meters from at least one of the transmission line conductors 224
and 226.
[0167] In the example shown in FIG. 21, transmission line
conductors 224 and 226 are in approximately horizontal arrangement
with one another. That is, transmission line conductors 224 and 226
are located at approximately the same depth from the surface. In
some embodiments, transmission line conductors can be in
approximately vertical arrangement with one another. That is,
transmission line conductors 224 and 226 can be located at
different depths. Also shown in FIG. 21, metal casings 166 and 168
may be provided to form non-radiating coaxial transmission lines to
prevent direct contact between the high frequency connectors 110
and 112 and the hydrocarbon formation along the vertical portion of
the high frequency connectors 110 and 112. While each metal casing
166 and 168 are depicted as being separated by the hydrocarbon
formations, in some embodiments, the casings carrying high
frequency connectors 110 and 112 can be joined together (e.g. via
welding or some other known joining method) in a manner similar to
casings 160 and 162 of FIGS. 23A, 24A and 24B.
[0168] Similar to the distance between the vertical pipes to the
transmission line conductors 224 and 226, the transmission line
conductors 224 and 226 can be located at any distance from one
another that is practical for the hydrocarbon formation 100 to be
heated by the interaction with the electromagnetic field. In some
embodiments, the transmission line conductors 224 and 226 can be
located within about 100 meters from one another. When the
transmission line conductors 224 and 226 are located at a far
distance from one another, the heating process takes more time.
Preferably, the transmission line conductors 224 and 226 can be
located within about 30 meters from one another. Further
preferably, the transmission line conductors 224 and 226 can be
located within about 3 to 25 meters from one another.
[0169] In addition, the distance between the transmission line
conductors 224 and 226 can vary along the dynamic transmission
line. A variation in the distance can be provided to increase the
heating time in particular areas where hydrocarbon deposits are
known, or to decrease the heating time in particular areas where
hydrocarbon deposits are uncertain. A variation in the distance can
also be required due to difficulties in the deployment process of
maintaining a uniform distance.
[0170] Referring to FIG. 22, there is a profile view of an
apparatus 23 according to at least one example embodiment. Features
common to apparatus 21 are shown using the same reference numbers.
As shown in FIG. 22, a first high frequency connector 110 can be
used as a waveguide for carrying high frequency alternating current
from the EM wave generator 92 to transmission line conductor 228
and a second high frequency connector 112 can be used as a
waveguide for carrying high frequency alternating current from the
EM wave generator 92 to transmission line conductor 230. While high
frequency connectors 110 and 112 are shown in FIG. 22 as being
substantially vertical (i.e., perpendicular to the surface), it
will be understood that in some embodiments, any one or both of
high frequency connectors 110 and 112, or sections thereof, can be
angled or curved with respect to the surface.
[0171] In contrast to transmission line conductors 224 and 226 of
apparatus 21, which have approximately consistent depths along the
hydrocarbon formation 100, transmission line conductors 228 and 230
can have varying depths along the hydrocarbon formation 100.
Varying depths along the hydrocarbon formation 100 can be
beneficial to enhance production. For example, the transmission
line conductors 228 and 230 may be positioned higher (i.e., less
depth) between the vertical pipe and lower (i.e., greater depth)
around the wells to take advantage of gravity or as a result of
difficulties in the deployment process of maintaining a particular
depth.
[0172] As shown in FIG. 22, at least one additional injecting well
158 can be provided to inject gaseous or liquid substances 148 into
the hydrocarbon formation to enhance production. Although not
shown, the transmission line conductors 228 and 230 can also be
used to inject gaseous or liquid substances 148 into the
hydrocarbon formation.
[0173] Referring to FIG. 23A, there is a cross-sectional view of an
apparatus 25 according to at least one example embodiment. Features
common to apparatus 13 and 23 are shown using the same reference
numbers. A first high frequency connector 110 can be used as a
waveguide for carrying high frequency alternating current from the
EM wave generator 92 to transmission line conductor 224 and a
second high frequency connector 112 can be used as a waveguide for
carrying high frequency alternating current from the EM wave
generator 92 to transmission line conductor 226. As set out above,
the high frequency connectors 110 and 112 can be routed through
metal casings 160 and 162 to form non-radiating coaxial
transmission lines and prevent direct contact between the high
frequency connectors 110 and 112. Each metal casing can be
electrically grounded 116 and 118 to prevent high frequency
alternating current from returning to the surface along the outer
surface of metal casings 166 and 168. Any one of high frequency
connectors 110 and 112, or sections thereof, can be substantially
vertical (i.e., perpendicular to the surface), angled or curved
with respect to the surface (not shown). In some embodiment, the
substantially vertically oriented high frequency connectors 110 and
112 can similarly be used in association with horizontally oriented
producers (not shown).
[0174] In contrast to the metal casings 166 and 168 of FIG. 15, the
metal casings 160 and 162 of FIG. 23A can be in electrical contact
with one another to provide a balun. Although the electrical
contact shown in FIG. 23A is continuous along the length of the
high frequency connectors 110 and 112, it can also be a single
point of contact. In some embodiments, the electrical contact can
be intermittent with at least one point of contact near each end of
the high frequency connectors 110 and 112 to form a closed circuit.
Electrical contact between metal casings 160 and 162 can be
provided by any appropriate means, including but not limited to,
welding or conductive connectors between the metal casings,
including metallic rings.
[0175] Similar to electrical short 46 between metal casing 28 and
30 of apparatus 1 (as shown in FIG. 1), a balun provided by metal
casings 160 and 162 in electrical contact with one another can
eliminate the need for chokes. Referring to FIGS. 25A and 25B,
there is a magnified cross-sectional view of a pair of metal
casings 166 and 168 that are not in contact with one another, and a
pair of metal casings 160 and 162 that are in contact with one
another. As shown in FIG. 25A, when metal casings 166 and 168 are
not in contact with one another, current on the inside surfaces of
the metal casings 166 and 168 can, at the distal end of the metal
casing, flow over to the outside surfaces of the metal casings 166
and 168. However, as shown in FIG. 25B, when metal casings 160 and
162 are in contact with one another, current on the inside surfaces
of the metal casings 160 and 162 can flow to one another,
eliminating current on the outside surface of the metal casings 160
and 162. Thus, a balun provided by metal casings 160 and 162 in
electrical contact with one another can be more effective than the
electrical short 46 of apparatus 1.
[0176] Referring to FIG. 23B, there is a cross-sectional view of an
apparatus 39 according to at least one example embodiment. Features
common to apparatus 13 and 25 are shown using the same reference
numbers. Similar to apparatus 25, high frequency connectors 110 and
112 in apparatus 39 can be routed through metal casings 160 and
162, which are in electrical contact with one another to provide a
balun. Similar to apparatus 13, apparatus 39 is used with a pair of
pipe strings that are substantially horizontal. In some
embodiments, producer 20 may, in other cross-sectional views of
apparatus 39, be located below and substantially symmetrically
positioned between transmission line conductors 226 and 227. The
transmission line conductors 226 and 227 in some cases may be
horizontally separated by a distance between 1 meter and 25 meters.
In some other embodiments, injector 22 may be excluded in apparatus
39.
[0177] Referring to FIG. 24A, there is a cross-sectional view of an
apparatus 27 according to at least one example embodiment. Features
common to apparatus 25 are shown using the same reference numbers.
Metal casings 160 and 162 can be routed through an additional metal
casing 164 to prevent direct contact with the hydrocarbon formation
100. In some embodiments, metal casings 160 and 162 can be routed
through separate additional metal casings (shown in FIGS. 45 and
47). In some embodiments, the substantially vertically oriented
high frequency connectors 110 and 112 can similarly be used in
association with horizontally oriented producers (not shown).
[0178] Referring to FIG. 24B, there is a cross-sectional view of an
apparatus 47 according to at least one example embodiment. Features
common to apparatus 27 are shown using the same reference numbers.
High frequency connectors 110 and 112 can be routed through a
single metal casing 164 to prevent direct contact between the high
frequency connectors 110 and 112 and the hydrocarbon formation 100.
Metal casing 164 can be electrically grounded 242 to prevent high
frequency alternating current from returning to the surface. In
some embodiments, the substantially vertically oriented high
frequency connectors 110 and 112 can similarly be used in
association with horizontally oriented producers (not shown).
[0179] A shielded two-wire transmission line is formed when high
frequency connectors 110 and 112 are routed through a single metal
casing 164 as shown in FIG. 24B. The EM wave power can be carried
in the annular space within the single metal casing 164 and between
the high frequency connectors 110 and 112. However, the power
capacity of the annular space can depend on the geometry and
materials within the annular space. A dielectric breakdown can
occur when the shielded two-wire transmission line is operated at
voltages that exceed the dielectric breakdown voltage of the
annular space between the high frequency connectors 110 and 112 and
the metal casing 164. In some embodiments, the annular space can be
filled with dielectric material 244 having a high dielectric
breakdown voltage to allow the shielded two-wire transmission line
to operate at higher voltages, thus increasing the power capacity
of the annular space. It will be understood that for increased
power capacity, such dielectric material 244 can be provided in the
annulus of any waveguide formed by high frequency connectors 110
and 112 routed through metal casings 160, 162, 166, or 168
disclosed herein.
[0180] Any appropriate dielectric material 244 having a high
dielectric breakdown voltage can be used. The dielectric material
244 can be gas, liquid, or solid including powders, or a
combination of gas, liquid, and/or solid. However, an apparatus 47
having a gaseous dielectric material 244 can be simpler to operate
than an apparatus 47 having a liquid dielectric material 244 due to
the challenges of filling the annular space with a liquid and
maintaining purity of the liquid. An example of a liquid dielectric
material 244 is hydrocarbons.
[0181] In some embodiments wherein the dielectric material 244 is a
gas, the gas can be pressurized to further provide a higher
dielectric strength than that of gas at atmospheric pressure. As
well, gas can have arc-quenching properties, particularly when it
is mixed with electronegative gases. For example, gases having
arc-quenching properties include carbon dioxide (CO.sub.2) and
nitrogen (N.sub.2). Electronegative gases can absorb free
electrons, thereby extinguishing current carried through an arc.
Examples of electronegative gases include, but are not limited to,
Sulfur hexafluoride (SF.sub.6), 1,1,1,2-Tetrafluoroethane
(C.sub.2H.sub.2F.sub.4), Octafluorocyclobutane (C.sub.4F.sub.8), a
mixture of any one of SF.sub.6, C.sub.2H.sub.2F.sub.4, and
C.sub.4F.sub.8. Electronegative gases can also be used on their
own, without being mixed with other gases such as nitrogen and/or
carbon dioxide. The gas used in the annulus can also be a mixture
of fluoroketone (C.sub.5F.sub.10O), oxygen (O.sub.2), and one of
CO.sub.2 or N.sub.2.
[0182] As shown in FIG. 24B, spacers or centralizers 174 can be
provided along the metal casing 164 to prevent direct contact
between the high frequency connectors 110 and 112 with metal casing
164 and to prevent or limit appreciable movement of high frequency
connectors 110 and 112 from designated locations.
[0183] Furthermore, spacers or centralizers 174 can be formed of
materials having high thermal conductivity to act as a thermal
bridge, or a heat spreader for the high frequency connectors 110
and 112. Any appropriate material having a thermal conductivity
between 0.5 and 2000 Watts per meter Kelvin (W/mK) may be used.
Examples of materials having high thermal conductivity include
ceramics (e.g., alumina and zirconia), reinforced ceramics, and a
combination of different ceramics. As well, spacers or centralizers
174 can be formed of high resistivity carbides. High frequency
connectors 110 and 112 can become very hot as they carry high
frequency alternating current from the EM wave generator 92 to
transmission line conductors 224 and 226. Such heat is generally
not dissipated by the annular space, especially when the annular
space is filled with a non-circulating gaseous dielectric material
244 having low thermal conductivity. Even if the annular space is
filled with circulating gaseous dielectric material 244 having low
thermal conductivity, circulation of the gaseous dielectric
material 244 must be provided at a sufficient volume, temperature,
and/or or speed to maintain the temperature of the high frequency
connectors 110 and 112 at appropriate levels.
[0184] Furthermore, spacers or centralizers 174 formed of material
having high thermal conductivity can lower the temperature of the
high frequency connectors 110 and 112 by conducting heat from the
high frequency connectors 110 and 112 to the metal casing 164. In
turn, the metal casing can dissipate the heat.
[0185] Apparatus 47 can include a seal 184 at a distal end of the
metal casing 164 to prevent fluids from entering the coaxial
transmission line formed by the high frequency connectors 110 and
112 and the metal casings 164. Seal 184 can be a dielectric shoe
joint or a packer. Furthermore, seal 184 can include a balancing
and/or a matching network to prevent current on the interior of the
metal casings 166 and 168 from flowing to the exterior of the metal
casings 166 and 168, and/or to match the impedance in the system
thus ensuring that the power flows to the transmission line
conductors 224 and 226.
[0186] Referring to FIG. 26, there is a profile view of the
deployment of coiled tubing for an apparatus for electromagnetic
heating of formations according to at least one embodiment. As set
out above, high frequency connectors 110 and 112 and transmission
line conductors 224 and 226 can be in the form of coiled tubing
172, as shown in FIG. 26. Coiled tubing 172 is a very long metal
pipe, supplied on a large spool 170. A coiled tubing injector head
176 can be used to dispense coiled tubing 172 from spool 170.
[0187] As a high frequency connector, coiled tubing 172 is routed
through metal casing 166. Similar to apparatus 47, spacers or
centralizers 174 can be provided along the routing to mechanically
and electrically isolate the coiled tubing 172 from the metal
casing 166.
[0188] Coiled tubing 172 is typically made of steel, which is an
inferior electrical conductor compared to other materials such as
copper and aluminum. In some embodiments, coiled tubing 172 can be
modified. More specifically, cladding can be provided along the
outer surface of the coiled tubing 172 to reduce electrical power
losses. The term "cladding", as used herein, broadly refers to one
or more layers of highly conductive material provided by cladding,
electroplating, or any other appropriate means. Cladding may cover
a portion of or the entire coiled tubing 172. Cladding may be
highly conductive metal with low magnetic permeability. Any
appropriate material may be used to provide cladding. For example,
cladding may be copper or aluminum.
[0189] In addition, an insulating dielectric coating can be applied
to the surface of the coiled tubing or the cladding. The insulating
dielectric coating can prevent the hydrocarbon formation of a
carbon path between the high frequency connector and the metal
casing, that is, between inner and outer conductors of the coaxial
transmission line, in the event of a partial or full dielectric
breakdown in the coaxial transmission line. A dielectric breakdown
can occur when the coaxial transmission line is operated at
voltages that exceed the dielectric breakdown voltage of the
insulation between the inner and outer conductors. In some
embodiments, gases or liquids with a high dielectric breakdown
voltage can be used as insulation between the inner and outer
conductors to allow the coaxial transmission line to operate at
higher voltages. For example, hydrocarbons or mixtures of
electronegative gases can provide a higher dielectric breakdown
voltage as set out above.
[0190] Similar to cladding, insulating dielectric coating may cover
a portion of or the entire coiled tubing 172. In some embodiments,
insulating dielectric coating can be applied to a select portion or
the entire length to achieve a pre-determined impedance or
temperature on the surface of the coiled tubing 172. The insulating
dielectric coating can be a dielectric paint or a wrapping tape.
Any appropriate material may be used to provide the insulating
dielectric coating. For example, wrapping tape may be formed of
Mylar.
[0191] Whether used as high frequency connectors or as transmission
line conductors, the interior of coiled tubing 172 is not used for
the transmission of RF or AC/DC power. In some embodiments, the
interior of coiled tubing 172 can be utilized for other purposes.
For example, sensors can be distributed along the transmission line
and within coiled tubing 172 for monitoring conditions including,
but not limited to temperature, pressure, petro-physical, and steam
properties.
[0192] In another example, fluids can be conveyed through the
interior of the coiled tubing 172. For example, fluids can serve as
coolants in critical sections of the transmission line. Fluids can
also fill or circulate the interior of the coiled tubing 172 to
purge the transmission line and increase the safety of the coiled
tubing 172. Furthermore, portions of, or the entire coiled tubing
172 can be a slotted line so that fluids conveyed in the interior
of the coiled tubing 172 can be injected into the hydrocarbon
formation 100 to enhance hydrocarbon production or to establish
particular properties of the transmission line. For example, in
some cases, gas injection through the coiled tubing 172 can
increase the pressure of the transmission line and/or maintain
control of the temperature of the coiled tubing 172
[0193] Referring to FIG. 27, there is a profile view of an
apparatus 6 with the exposed, or partially exposed, or partially
insulated, transmission line conductors 20 and 22 according to at
least one example embodiment. Referring to FIG. 28, there is a
profile view of an apparatus 6 with fully exposed transmission line
conductors 20 and 22 according to at least one example embodiment.
Partially exposed, or partially insulated transmission line
conductors 20 and 22 would also have a similar profile view as that
shown in FIG. 28 after operation for some time.
[0194] Whether the transmission line conductors 20 and 22 are
insulated or non-insulated, the hydrocarbon formation 100 around
the transmission line conductors 20 and 22 is heated 130 and 132
and can eventually desiccate. Water within the hydrocarbon
formation 100 can be heated to steam and hydrocarbons can be
released. These changes can cause a change in the dielectric
parameters of the hydrocarbon formation 100 acting as the core of
the dynamic transmission line. More specifically, these changes can
lower the permittivity and conductivity of the hydrocarbon
formation 100, resulting in significantly a lower complex
dielectric constant around the transmission line with respect to
that of the hydrocarbon formation 100.
[0195] As a result, the EM signal carried by the dynamic
transmission line can travel faster in the dynamic transmission
line than in the surrounding medium, which can still be colder and
rich in water. This can lead to an electromagnetic phenomenon known
as a fast wave, in which the phase velocity in the transmission
line is faster than in the surrounding medium.
[0196] When a fast wave occurs, and the transmission line is open,
the radiation process that occurs is generally known as leaky wave
radiation. Thus, the dynamic transmission line can operate as an
open transmission line as well as a radiating antenna. After
initially operating as a simple, lossy transmission line
propagating an electromagnetic wave in the hydrocarbon formation,
the dynamic transmission line transitions to a leaky wave antenna
radiating EM waves into the hydrocarbon formation. FIGS. 29 and 30
illustrate leaky wave radiation can develop 136 and further enhance
138 the heat penetration 134 of the wave into the hydrocarbon
formation 100.
[0197] Depending on the stage of operation, the apparatus may be
operated at different frequencies to achieve particular heating
patterns. For example, in some embodiments, the apparatus may be
operated at lower frequencies early in the heating process to
accelerate the hydrocarbon formation of a desiccated region between
the transmission line conductors or to maintain a more homogenous
heating pattern along the length of the dynamic transmission line.
However, in some embodiments, the apparatus may be operated at
higher frequencies later in the heating process to promote more
efficient leaky wave radiation, to increase the electrical length
(i.e., the length in relation to wavelength), or to periodically
change the frequency. Periodically changing the frequency can be
performed to address potential standing wave issues. More
specifically, in certain stages of the heating process, not all of
the power of the traveling wave will be absorbed by or radiated
into the hydrocarbon formation before the traveling wave reaches
the distal end of the dynamic transmission line. Instead, a certain
fraction of the traveling wave may reach the distal end of the
dynamic transmission line and reflect back from it, creating a
standing wave. The standing wave is typically visible only in a
section of the dynamic transmission line, close to its distal end.
However, it may also occupy a larger portion of the dynamic
transmission line, especially when a significant portion of the
hydrocarbon formation around the dynamic transmission line is
desiccated. Standing waves can cause non-homogenous heating along
the length of the dynamic transmission line. Changing the frequency
can move the standing wave nodes along the length of the dynamic
transmission line. Alternatively, more than one signals having
different frequencies can be used. As well, non-sinusoidal signals
that have harmonics, such as square waveform, can be used. Higher
order harmonics may operate better as a leaky wave antenna.
[0198] Referring to FIGS. 31A to 31C, there shown is a temperature
distribution of a fully insulated dynamic transmission line. As set
out above, pipe sections can be fully insulated as shown in FIGS.
11D, 12A, and 12B. Relatively lower power may be used when the
dynamic transmission line is fully insulated. However, high power
can accelerate the heating process. As shown in FIGS. 31A to 31C,
heating develops uniformly along the fully insulated dynamic
transmission line. The uniform heating achieved by a fully
insulated dynamic transmission line may be useful for SAGD
preheating applications.
[0199] Referring to FIGS. 32A to 32C, there shown is a heat
delivery distribution of a non-insulated dynamic transmission line.
With a non-insulated dynamic transmission line, transmission line
conductors 20 and 22 are not insulated. The dynamic transmission
line forms a highly lossy transmission line, characterized by a
significant attenuation constant. Initially, at day 1 (shown in
FIG. 32A), EM energy dissipates rapidly at the proximal end of the
transmission line conductors 20 and 22, which quickly desiccates
the hydrocarbon formation at the proximal end of the transmission
line conductors 20 and 22. The desiccation creates a low loss
layer, which lowers the attenuation constant. The lower attenuation
constant allows the electromagnetic wave to propagate further down
the dynamic transmission line and towards the distal end of the
transmission line conductors 20 and 22.
[0200] As time progress, as shown after 100 days of operation in
FIG. 32B, the heated area progresses further along the dynamic
transmission line. After 200 days of operation (shown in FIG. 32C),
most areas along the transmission line conductors 20 and 22 are
heated. Although heat is dissipated along the entire length of the
transmission line conductors 20 and 22, a standing wave pattern can
develop and reduce the heat at the distal end of the transmission
line conductors 20 and 22.
[0201] Referring to FIGS. 33A to 33B, there shown is the electric
field on the first day of operation of a dynamic transmission line.
As shown in FIG. 33A, the electric field is carried along the
length of a fully-insulated dynamic transmission line. In contrast,
the electric field of a non-insulated dynamic transmission line is
shown in FIG. 33B.
[0202] Referring to FIGS. 34A to 34B, the temperature distribution
of a semi-insulated dynamic transmission line after 1 and 20 days
of EM heating is shown. As set out above, pipe sections can be
partially insulated as shown in FIG. 11B. In this simulation, the
length of exposed portions of the metallic pipe sections was longer
than typical. Initially, at day 1 (shown in FIG. 34A), the
temperature distribution can be similar to that of a non-insulated
dynamic transmission line. At approximately day 20 (shown in FIG.
34B), the EM power can propagate to the entire length of the
transmission line conductor. As a result, the temperature
distribution can be similar to that of an insulated dynamic
transmission line.
[0203] Referring to FIGS. 35A to 35F, various pipe configurations
are shown that can be utilized in the present apparatus. The
various pipe configuration examples can be used for at least one of
the dynamic transmission line conductors to improve the heating
coverage of the present apparatus. FIG. 35A shows pipe
configuration 300 having an inverted "T" junction. Configuration
300 includes a vertical pipe portion 302 and two horizontal pipe
portions 304 and 306 that extend from the vertical pipe portion 302
in opposite directions.
[0204] FIG. 35B shows pipe configuration 310 having an inverted "F"
junction. Configuration 310 includes a vertical pipe portion 312
and two horizontal pipe portions 314 and 316 that extend from the
vertical pipe portion 312 in the same direction. Horizontal pipe
portions 314 and 316 can be located above one another.
[0205] FIG. 35C shows pipe configuration 320 having a vertical pipe
portion 322. Two horizontal pipe portions 324 and 326 can extend
from the vertical pipe portion 322 in the same direction.
Horizontal pipe portions 324 and 326 can be located at the same
height and parallel to one another.
[0206] FIG. 35D shows pipe configuration 330 having a vertical pipe
portion 332. Three horizontal pipe portions 334, 336, and 338 can
extend from the vertical pipe portion 332 in the same direction.
Similar to FIG. 35C, horizontal pipe portions 334, 336, and 338 can
be located at the same height and parallel to one another.
[0207] FIG. 35E shows pipe configuration 340 having a vertical pipe
portion 342. Four horizontal pipe portions 344, 346, 348, and 350
can extend from the vertical pipe portion 342 in opposite
directions. Horizontal pipe portions 344, 346, 348, and 350 can be
located at the same height as one another.
[0208] FIG. 35F shows pipe configuration 360 having fishbone
junction. Configuration 360 includes a vertical pipe portion 352
that transitions to a horizontal pipe portion 368. Six horizontal
pipe portions 354, 356, 358, 362, 364, and 366 can extend at an
angle from the horizontal pipe portion 368.
[0209] Referring to FIGS. 36 and 37, there is a schematic and
perspective view of an apparatus 29 according to at least one
example embodiment. As shown in FIG. 36, apparatus 29 includes a
pair of apparatus 27 (shown in FIG. 24A). Features of each
apparatus 27 are shown using the same reference numbers and
indicated by the letter suffix `a` for the first apparatus and the
letter suffix `b` for the second apparatus 27. Metal casings 160a
and 162a of the first apparatus 27 are in electrical contact and
metal casings 160b and 162b of the second apparatus 27 are in
electrical contact. Well platform 178 can be one or more platforms
located at the surface, or above ground and at the proximal end of
metal casings 160a, 162a, 160b, and 162b. While apparatus 29 is
described as being a pair of apparatus 27, it will be understood
that any one or both apparatus 27 can also be apparatus 25 (shown
in FIG. 23A), apparatus 39 (shown in FIG. 23B), or apparatus 47
(shown in FIG. 24B).
[0210] As shown in FIG. 36, apparatus 29 includes two EM wave
generators 166a and 166b. In some embodiments, EM wave generator
166a can generate a sinusoidal signal and EM wave generator 166b
can generate a sinusoidal signal that is a 180.degree.
phase-shifted version of the sinusoidal signal generated by EM wave
generator 166a. In some embodiments, only one EM wave generator can
be provided to excite the first apparatus 27 and the second
apparatus 27. The EM wave generators 166a and 166b can be located
above ground (not shown). The EM wave generators 166a and 166b can
each include an inverter, a pulse synthesizer, a transformer, one
or more switches, a low-to-high frequency converter, an oscillator,
an amplifier, or any combination of one or more thereof.
[0211] In FIG. 36, current at a time instant is illustrated by
solid arrows and the electric field at a time instant is
illustrated by dashed arrows. As shown in FIG. 36, current travels
along transmission line conductor 224a in a direction opposite to
that of transmission line conductor 224b and together, transmission
line conductors 224a and 224b form a first dynamic transmission
line. Similarly, current travels along transmission line conductor
226a in a direction opposite to that of transmission line conductor
226b and together, transmission line conductors 226a and 226b form
a second dynamic transmission line.
[0212] Different materials can exist in a hydrocarbon formation.
For example, there can an interface or boundary between wet and dry
materials or when the hydrocarbon formation is stratified. As shown
in FIG. 36, electric fields between the dynamic transmission lines
are generally in a direction that is normal to the direction of
current travelling along each transmission line conductor. However,
when electric fields penetrate an interface between two different
materials at an angle that is perpendicular to the interface, power
transmission can be diminished, resulting in less heating of the
hydrocarbon formation.
[0213] Apparatus 29 includes at least one producer pipe. As shown
in FIG. 37, the at least one producer pipe can be an SAGD pipe,
similar to pipe 20 and 22 of apparatus 13 in FIGS. 14 and 15. As
shown in FIG. 37, pipe 20 can be situated substantially parallel to
the dynamic transmission lines. Furthermore, the pipe 20 can be
located below, above, or in between the transmission line
conductors of the dynamic transmission lines. In some embodiments,
the at least one producer pipe of apparatus 29 can be a vertical
pipes, similar to pipes 150, 152, 154, and 156 of apparatus 21 in
FIGS. 20 and 21.
[0214] As shown in FIG. 37, the dynamic transmission lines can be
arranged in an approximately vertical arrangement. That is,
transmission line conductors 224a and 226a can be located at
different depths from 224b and 226b, respectively. In some
embodiments, the dynamic transmission lines can be arranged in an
approximately horizontal arrangement. That is, transmission line
conductors 224a and 226a can be located at approximately the same
depth from the surface as transmission line conductors 224b and
226b, respectively. It will be understood that transmission line
conductors 224b and 226b can have any other appropriate arrangement
as disclosed herein. For example, the distance between transmission
line conductors 224b and 226b can be varying.
[0215] The transition between the distal end of the high frequency
connectors and the transmission line conductors can be any
appropriate angle. The angle can depend on the drilling technology.
As shown in FIG. 37, the transition between high frequency
connectors 110b and 112b to transmission line conductors 224b and
224b is a 90.degree. bend while the transition between high
frequency connectors 110a and 112a to transmission line conductors
224b and 224b is an arch.
[0216] Referring to FIG. 38, there is a schematic view of an
apparatus 31 according to at least one example embodiment. Features
common to apparatus 29 are shown using the same reference numbers.
Apparatus 31 includes two EM wave generators that can generate
identical signals which are substantially in phase (i.e., phase
difference of 0.degree.), or have no appreciable delay between the
signals.
[0217] Similar to FIG. 36, current at a time instant is illustrated
by solid arrows and the electric field at a time instant is
illustrated by dashed arrows in FIG. 38. Current travels along
transmission line conductor 224a in a direction that is the same as
that of transmission line conductor 224b. As well, current travels
along transmission line conductor 226a in a direction that is the
same as that of transmission line conductor 226b. Hence, apparatus
31 can operate as a dipole antenna with transmission line
conductors 224a and 224b forming a first arm of the dipole antenna
and transmission line conductors 226a and 226b forming a second arm
of the dipole antenna. Apparatus 31 can also be viewed as a system
of two dipole antennas in which transmission line conductors 224a
and 226b form a first dipole antenna and transmission line
conductors 224b and 226b form a second dipole antenna. When
operating as a single or double dipole antenna, apparatus 31 can
resonate a standing wave within the hydrocarbon formation 100.
[0218] Since transmission line conductors of each arm are
symmetrically excited, the dipole antenna does not require chokes
or additional baluns to eliminate unwanted or common mode currents.
Producer pipes (not shown), such as SAGD pipes 20 and 22 of
apparatus 13 of FIGS. 14 and 15, can be situated substantially
parallel to the dipole antenna. Furthermore, the producer pipes can
be located below, above, or in between the transmission line
conductors of the dipole antenna.
[0219] As shown at a time instant in FIG. 38, when operating as a
dipole antenna, electric fields between the transmission line
conductors are generally in a direction that is parallel to the
direction of current travelling along each transmission line
conductor. As set out above, when electric fields penetrate an
interface between two different materials at an angle that is
perpendicular to the interface, power transmission can be
diminished, resulting in less heating of the hydrocarbon formation.
Such power losses can be reduced if electric fields penetrate an
interface between two different materials at an angle that is
substantially parallel to the interface, allowing for better
heating.
[0220] EM wave generator 166b of FIG. 36 can be converted to EM
wave generator 166c of FIG. 38 by switching the terminals that each
transmission line conductor is connected to. The terminals can be
switched at the surface, that is, above ground. The ease of
conversion between EM wave generator 166b and 166c can allow
apparatuses 29 and 31 to be used interchangeably, depending on the
structure of the hydrocarbon formation. It may be desirable to
change the operation from apparatus 29 to apparatus 31 or vice
versa as the heating process progresses. For example, it may be
desirable to initially use apparatus 29 to initiate production and
evaporate water from between the transmission line conductors 224
and 226 and then change to apparatus 31 to achieve radiation
characteristic typical of a dipole antenna.
[0221] Referring to FIG. 39, there is a schematic view of an
apparatus 33 according to at least one example embodiment. Features
common to apparatus 29 are shown using the same reference
numbers.
[0222] As shown in FIG. 39, apparatus 33 includes two EM wave
generators that are out of phase. The phase difference between EM
wave generator 92a and 92b is not limited to 180.degree. (similar
to apparatus 29 in FIG. 36) or 0.degree. (similar to apparatus 31
in FIG. 38). The phase difference between EM wave generator 92a and
92b can be any phase between 0.degree. to
360.degree..+-.(n.times.360.degree.), where n is any integer. For
example, EM wave generator 92a and 92b can be 90.degree. out of
phase and apparatus 33 will not operate as dynamic transmission
line nor a dipole antenna.
[0223] FIGS. 40A to 40H show cross-sectional views of the electric
field of apparatus 31 along cross-section A-A' in FIG. 39 at
sequential time instants, namely at 45.degree. phase shift
increments. As shown in FIGS. 40A to 40H, the electric field
rotates as the phase shifts.
[0224] The rotation of the electric field depends on the EM waves
provided by EM wave generators 92a and 92b. Since the EM waves
generated by EM wave generators 92a and 92b are 90.degree. out of
phase, the vector amplitude of each waveform is different at any
time instant. The amplitude of the EM waves can also be different
at any time instant due to different waveforms generated by EM wave
generators 92a and 92b. Furthermore, the amplitude can also
diminish as the EM wave propagates in the hydrocarbon formation.
Thus, the relative amplitude of the EM waves can vary due to the
spatial geometry of the transmission line conductors.
[0225] The electric field shown in FIGS. 40A to 40H can be
characterized as having an elliptical polarization. Such an
elliptical polarization of the electric field can at least occur in
some location within the hydrocarbon formation. An elliptical
polarization can be suitable for heating formation that is
stratified because the electric field can better penetrate
interfaces between different materials.
[0226] Referring to FIG. 41, there is a schematic view of an
apparatus 35 according to at least one example embodiment. Features
common to apparatus 29 and 33 are shown using the same reference
numbers. The EM wave generators 92a and 92b of apparatus 35 in FIG.
41 can generate EM waves that are 180.degree. out of phase, similar
to EM wave generators 166a and 166b of apparatus 29, substantially
in phase, similar to EM wave generators 166a and 166c of apparatus
31, or have any other phase difference. The apparatus can operate
as a dipole antenna, as a dynamic transmission line, or combination
of the dipole antenna and the dynamic transmission line.
[0227] While transmission line conductors 224a and 224b are shown
in FIG. as being substantially parallel to one another, in some
embodiments, transmission line conductors 224a and 224b can diverge
from each other at any angle. Similarly, while transmission line
conductors 232a and 232b are shown in FIG. 41 as diverging from
each other, in some embodiments, transmission line conductors 232a
and 232b can be substantially parallel to one another. It can be
preferable for the transmission line conductors to diverge from one
another in order to heat a larger volume of the hydrocarbon
formation.
[0228] Referring to FIG. 42, there is a schematic view of an
apparatus 49 according to at least one example embodiment. Features
common to apparatus 29 and 33 are shown using the same reference
numbers. Similar to the transmission line conductors of apparatus
29 and 33, transmission line conductors 224c and 224d as well as
226c and 226d are substantially parallel to one another. It may be
noted that the difference between apparatus 49 and apparatus 29 and
33 is that in the present case, the two arms of the two arms of the
transmission lines 224c, 224d, 226c, 226d are parallel to each
other as opposed to pointing away from each other. Generally, such
a configuration is not likely to be operational in free space.
However, when deployed within a hydrocarbon formation, the
formation can sufficiently attenuate the irradiated power such that
the transmission line pairs 226c and 226d, and 224c and 224d do not
couple. In this case, the transmission line pairs can behave as if
they are in a straight configuration similar to the apparatus of
FIG. 39. In some embodiments, the present apparatus can be applied
in normal wells, in which creation of the well involves drilling
from the surface first vertical holes and then directional vertical
holes (e.g. for deployment of transmission line conductors). In
this case, the sections of the transmission line conductors which
are depicted as horizontally oriented in FIG. 42 can be curved and
partially vertical.
[0229] In order for apparatus 49 to operate as a dipole antenna
with transmission line conductors 224c and 224d forming a first arm
of the dipole antenna and transmission line conductors 226c and
226d forming a second arm of the dipole antenna, sufficient
distance between the first and second arms of the dipole is
required to ensure that interaction between the first and second
arms is weak. A dipole antenna with substantially horizontal dipole
arms can be suitable for mine-face accessible hydrocarbon
formation. In the case of mine-face accessible hydrocarbon
formation, where drilling can be done from the side into the
hydrocarbon formation, then the orientation of the transmission
line pairs can be horizontal.
[0230] Referring to FIG. 43, there is a schematic view of an
apparatus 37 according to at least one example embodiment. Features
common to apparatus 27 are shown using the same reference numbers.
Similar to apparatus 27, apparatus 37 includes only one EM wave
generator 92 located above ground, or at the surface. The
deployment of apparatus 37 is simpler than apparatuses with two EM
wave generators, such as apparatuses 29, 31, 33, and 35.
[0231] Transmission line conductor 234 can be a producer pipe.
Similar to pipe 20 of apparatus 17 in FIGS. 18 and 19, transmission
line conductor 234 is not connected to EM wave generator 92. EM
wave generator 92 is connected to and excites transmission line
conductors 224 and 226, which can in turn, induce a current on
transmission line conductor 234. The excitation of apparatus 37 can
be characterized as a combined dipole/transmission line
excitation.
[0232] The operation of apparatus 37 is similar to a folded dipole
with the exception that in a folded dipole, suppression of the
transmission line mode is typically preferred. When heating
formations, it is desirable for the transmission line mode to
propagate.
[0233] Referring to FIG. 44, another transmission line conductor
arrangement is shown. Depending on the excitation of the
transmission line conductors, different transmission line conductor
arrangements can operate in different dipole configurations.
[0234] FIG. 44 shows a schematic view of an apparatus 41 according
to at least one example embodiment. Features common to apparatus 35
and 37 are shown using the same reference numbers. Similar to
apparatus 35, apparatus 41 can include two EM wave generators 92a
and 92b. EM wave generator 92a can excite transmission line
conductors 232a and 224a while second EM wave generator 92b can
excite transmission line conductors 226b and 232b.
[0235] Similar to apparatus 37, apparatus 41 can include
transmission line conductor 234 which is not connected to EM wave
generators 92a or 92b. Transmission line conductor 234 can be
situated between the transmission line conductors of each arm,
namely between 224a and 232c of a first arm and between 232a and
226b of a second arm. With transmission line conductor 234 situated
between the transmission line conductors of each arm, the
excitation of the first and second arms can induce a current on
transmission line conductor 234.
[0236] As shown in FIG. 44, the pair of transmission line
conductors forming an arm of the dipole antenna can be oriented in
different directions. Transmission line conductors 224a and 232c
forming the first arm of the dipole antenna are not substantially
parallel. Likewise, transmission line conductors 232a and 226b
forming the second arm of the dipole antenna are not substantially
parallel.
[0237] Referring to FIG. 45, there is a profile view of an
apparatus 45 according to at least one example embodiment. Features
common to apparatus 1, 21, 33, and 47 are shown using the same
reference numbers.
[0238] Similar to apparatus 33, apparatus 45 includes two EM wave
generators 92a and 92b located above ground, or at the surface. EM
wave generators 92a and 92b can be in phase or out of phase, with
any appropriate phase difference. Each EM wave generator 92a and
92b can excite a high frequency connector 110 and 112.
[0239] Each high frequency connector 110 and 112 can be situated
within a metal casing 166 and 168 to prevent direct contact between
the high frequency connectors 110 and 112 and the hydrocarbon
formation 100. Each metal casing 166 and 168 can be electrically
grounded (not shown) to prevent high frequency alternating current
from returning to the surface. Optionally, each metal casing 166
and 168 can be concentrically surrounded by a separation medium 36
and 38, similar to FIG. 1.
[0240] As well, an additional casing 180 and 182 that further
concentrically surrounds the separation medium 36 and 38 can be
provided. As shown in FIG. 45, the additional casing 180 and 182
can surround only a portion of the length of the metal casing 166
and 168. In some embodiments, casings 180 and 182 can be
approximately 50 meters to 60 meters in length. Casings 180 and 182
can be provided to allow for easier drilling of SAGD wells. When
casings 180 and 182 are used, they are typically drilled and
cemented first, and then used to direct drill bits for drilling
smaller wellbores for metal casings 168 and 166. While the
additional casings 180 and 180 do generally not regarded as having
significance electrically, in some embodiments, however, these
casings may be utilized as a safety chokes, if needed.
[0241] Since metal casings 166 and 168 are not in electrical
contact with one another (as shown in FIG. 25A), common mode
currents can occur. To eliminate the common mode currents, chokes
188 and 190 are provided. As shown in FIG. 45, chokes 188 and 190
can be situated at the distal end of metal casings 166 and 168.
When chokes 188 and 190 are sleeve type chokes and situated at the
distal end of metal casings 166 and 168, the upper end of the
choke, that is, the end that interfaces with separation medium 36
and 38 is the point at which current terminates. Such chokes that
terminate current at an upper end of the choke are herein referred
to as "inverted chokes".
[0242] When EM wave generators 92a and 92b are in phase, apparatus
43 can operate as a dipole antenna wherein pipes 20 and 22 form a
first arm and the external surfaces of chokes 188 and 190 form a
second arm. When EM wave generators 92a and 92b are 180.degree. out
of phase, apparatus 43 can operate as a dynamic transmission line.
Apparatus 43 can operate as a combination of a dipole antenna and
as a dynamic transmission line when EM wave generators 92a and 92b
have a phase difference other than 180.degree..
[0243] As shown in FIG. 45, apparatus 43 can include seals 184 and
186 to prevent fluids from entering the coaxial transmission line
formed by the high frequency connectors 110 and 112 and the metal
casings 166 and 168. Seals 184 and 186 can be provided to plug the
coaxial transmission line and block substances from entering the
coaxial transmission line, to keep pressurized fluids provided
inside the transmission line from leaking out, or both. More
specifically, seals 184 and 186 can block solids, liquids, and
gases from the hydrocarbon formation from entering metal casings
166 and 168. Seals 184 and 186 can be inert, or not chemically
reactive, to such solids, liquids and gases from the hydrocarbon
formation. If seals 184 and 186 are chemically reactive to solids,
liquids and gases from the hydrocarbon formation, the seals 184 and
186 may disintegrate over time. Seals 184 and 186 are generally
formed of insulating material to avoid a short-circuit between the
inner and outer conductors of the coaxial transmission line.
[0244] FIG. 46 is a perspective view of an inverted sleeve choke
188 of apparatus 43 according to at least one example embodiment.
As a sleeve choke, choke 188 can be a metal pipe that
concentrically surrounds the metal casing 166. Choke 188 can form a
short-circuited coaxial transmission line, wherein metal casing 166
is the inner conductor of the coaxial transmission line and the
choke is the outer conductor of the coaxial transmission line. The
lower end 238 of the choke can be short circuited. That is, metal
casing 166 can be in electrical contact with choke 188 at the lower
end 238.
[0245] The electrical length of the choke can be characterized in
terms of the wavelength of the EM wave inside the choke
(.lamda..sub.in) or the wavelength of the EM wave outside the choke
(.lamda..sub.out). In terms of the wavelength of the EM wave inside
the choke, the electrical length of the choke is approximately an
odd multiple of .lamda..sub.in/4. In terms of the wavelength of the
EM wave outside the choke, the electrical length of the choke is
approximately in the range of about .lamda..sub.out/50 to about
.lamda..sub.out.
[0246] To achieve the appropriate electrical length, space 240
between the metal casing 166 and choke 188 may be filled with
different dielectric and magnetic materials. Dielectric materials
can be liquids, such as hydrocarbon liquids (e.g., saraline,
toluene, benzene, etc.) or solids, such as glass or ceramic balls
made of zirconia or alumina. Magnetic materials can be various
ferrite ceramics or powders, etc.
[0247] In some embodiments, the appropriate electrical length can
also be achieved by providing corrugations on the inner and/or
outer conductors of the coaxial cable. More specifically, the inner
surface of the outer conductor and/or outer surface of the inner
conductor can be engraved with teeth to extend the path of the
current. The teeth can have any appropriate shape, for example,
rectangular or triangular.
[0248] Referring to FIG. 47, there is a profile view of an
apparatus 45 according to at least one example embodiment. Features
common to apparatus 43 are shown using the same reference numbers.
As shown in FIG. 47, chokes 196 and 198 can be situated along the
metal casings 166 and 168, providing choke shifts 192 and 194 at
the distal end of metal casings 166 and 168. When choke shifts 192
and 194 are provided, current can terminate at the upper ends and
the lower ends of chokes 196 and 198. Hence, chokes 196 and 198 can
be other types of chokes besides inverted chokes. For example,
chokes 196 and 198 can be regular bazooka chokes. Furthermore,
choke shifts 192 and 194 can be a part of the radiating
structure.
[0249] Referring to FIG. 48A, there is shown a method 1000 for
electromagnetic heating of a hydrocarbon formation in accordance
with some example embodiments. Method 1000 begins with providing
electrical power to at least one EM wave generator at 1010. At
1020, the at least one EM wave generator can be used to generate
high frequency alternating current. At 1030, at least one pipe can
be used to define at least one of at least two transmission line
conductors. At 1040, the at least two transmission line conductors
can be coupled to the at least one EM wave generator.
[0250] Referring to FIG. 48B, there is shown a method 1040 for
coupling the at least two transmission line conductor to the at
least one EM wave generator in accordance with some example
embodiments. Method 1040 begins with providing at least one
waveguide at 1042. Each of the at least one waveguide can have a
proximal end and a distal end. At 1044, the at least one proximal
end of the at least one waveguide can be connected to the at least
one EM wave generator. At 1046, the at least one distal end of the
at least one waveguide can be connected to one of the at least two
transmission line conductors.
[0251] Returning to FIG. 48A, at 1050, the high frequency
alternating current is applied to the at least two transmission
line conductors to excite the at least two transmission line
conductors. The excitation of the at least two transmission line
conductors propagates an electromagnetic wave within the
hydrocarbon formation.
[0252] At 1060, the method involves determining that a hydrocarbon
formation between the at least two transmission line conductors is
desiccated. A hydrocarbon formation can be determined to be
desiccated by measuring impedance at the proximal end of the at
least one waveguide. If the impedance is within a threshold
impedance, the hydrocarbon formation between the at least two
transmission line conductors can be determined to be desiccated;
otherwise the hydrocarbon formation between the at least two
transmission line conductors can be determined to not be
desiccated. In some embodiments, the threshold impedance represents
60% desiccation. The threshold impedance is determined based on the
material of the hydrocarbon formation and the electrical length of
the dynamic transmission line. The threshold impedance may be
determined based on the impedance initially measured before
operation of the dynamic transmission line. In some embodiments,
the threshold impedance represents a 50% reduction in the imaginary
part of the characteristic impedance of the dynamic transmission
line. In some embodiments, the threshold impedance represents a
100% increase in the reactive part of the measured impedance.
[0253] In some embodiments, a hydrocarbon formation can be
determined to be desiccated by measuring the temperature along at
least two transmission line conductors and at multiple points
between the at least two transmission line conductors. If the
temperatures at these points are above the steam saturation
temperature in the hydrocarbon formation, the hydrocarbon formation
at these points, located between the at least two transmission line
conductors, can be determined to be desiccated; otherwise, the
hydrocarbon formation between the at least two transmission line
conductors can be determined to not be desiccated. Given the
heterogeneity of the hydrocarbon formation and the nature of the
heating process, generally not all points become desiccated at the
same time. However, when the measured temperatures at all the
points between the transmission line conductors are above the steam
saturation temperature, it may then be said that the area becomes
desiccated.
[0254] At 1070, a radiofrequency electromagnetic current is applied
to the at least two transmission line conductors to excite the at
least two transmission line conductors. Electromagnetic waves of
the radiofrequency electromagnetic current radiates from the at
least two transmission line conductors to a hydrocarbon formation
surrounding the at least two transmission line conductors. The
radiofrequency electromagnetic current comprises an electromagnetic
power having a frequency between about 1 kilohertz (kHz) to about
10 megahertz (MHz). Any appropriate frequency between 1 kHz and 10
MHz may be used.
[0255] Numerous specific details are set forth herein in order to
provide a thorough understanding of the exemplary embodiments
described herein. However, it will be understood by those of
ordinary skill in the art that these embodiments may be practiced
without these specific details. In other instances, well-known
methods, procedures and components have not been described in
detail so as not to obscure the description of the embodiments.
Furthermore, this description is not to be considered as limiting
the scope of these embodiments in any way, but rather as merely
describing the implementation of these various embodiments.
* * * * *